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Sample records for aided fundamental atomistic

  1. Atomistic simulations of nanoindentation

    Directory of Open Access Journals (Sweden)

    Izabela Szlufarska

    2006-05-01

    Full Text Available Our understanding of mechanics is pushed to its limit when the functionality of devices is controlled at the nanometer scale. A fundamental understanding of nanomechanics is needed to design materials with optimum properties. Atomistic simulations can bring an important insight into nanostructure-property relations and, when combined with experiments, they become a powerful tool to move nanomechanics from basic science to the application area. Nanoindentation is a well-established technique for studying mechanical response. We review recent advances in modeling (atomistic and beyond of nanoindentation and discuss how they have contributed to our current state of knowledge.

  2. AIDS

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/000594.htm HIV/AIDS To use the sharing features on this page, ... immunodeficiency virus (HIV) is the virus that causes AIDS. When a person becomes infected with HIV, the ...

  3. Parallel Atomistic Simulations

    Energy Technology Data Exchange (ETDEWEB)

    HEFFELFINGER,GRANT S.

    2000-01-18

    Algorithms developed to enable the use of atomistic molecular simulation methods with parallel computers are reviewed. Methods appropriate for bonded as well as non-bonded (and charged) interactions are included. While strategies for obtaining parallel molecular simulations have been developed for the full variety of atomistic simulation methods, molecular dynamics and Monte Carlo have received the most attention. Three main types of parallel molecular dynamics simulations have been developed, the replicated data decomposition, the spatial decomposition, and the force decomposition. For Monte Carlo simulations, parallel algorithms have been developed which can be divided into two categories, those which require a modified Markov chain and those which do not. Parallel algorithms developed for other simulation methods such as Gibbs ensemble Monte Carlo, grand canonical molecular dynamics, and Monte Carlo methods for protein structure determination are also reviewed and issues such as how to measure parallel efficiency, especially in the case of parallel Monte Carlo algorithms with modified Markov chains are discussed.

  4. Atomistic simulations of fracture

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, D. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering

    1997-12-31

    Embedded atom interaction potentials are used to simulate the atomistic aspects of the fracture process. Simulations are presented for the behavior of cracks in pure metals and intermetallics, near the Griffith condition. The materials considered include Fe, Cu, Ni as well as Fe, Ni, Co, and Ti aluminides. The work focuses on the comparative study of fracture behavior in the different materials. The role of the atomic relaxation at the crack tip and of lattice trapping phenomena is analyzed.

  5. Integrated computer-aided design in automotive development development processes, geometric fundamentals, methods of CAD, knowledge-based engineering data management

    CERN Document Server

    Mario, Hirz; Gfrerrer, Anton; Lang, Johann

    2013-01-01

    The automotive industry faces constant pressure to reduce development costs and time while still increasing vehicle quality. To meet this challenge, engineers and researchers in both science and industry are developing effective strategies and flexible tools by enhancing and further integrating powerful, computer-aided design technology. This book provides a valuable overview of the development tools and methods of today and tomorrow. It is targeted not only towards professional project and design engineers, but also to students and to anyone who is interested in state-of-the-art computer-aided development. The book begins with an overview of automotive development processes and the principles of virtual product development. Focusing on computer-aided design, a comprehensive outline of the fundamentals of geometry representation provides a deeper insight into the mathematical techniques used to describe and model geometrical elements. The book then explores the link between the demands of integrated design pr...

  6. Atomistic Properties of Solids

    CERN Document Server

    Sirdeshmukh, Dinker B; Subhadra, K G

    2011-01-01

    The book deals with atomistic properties of solids which are determined by the crystal structure, interatomic forces and atomic displacements influenced by the effects of temperature, stress and electric fields. The book gives equal importance to experimental details and theory. There are full chapters dedicated to the tensor nature of physical properties, mechanical properties, lattice vibrations, crystal structure determination and ferroelectricity. The other crystalline states like nano-, poly-, liquid- and quasi crystals are discussed. Several new topics like nonlinear optics and the Rietveld method are presented in the book. The book lays emphasis on the role of symmetry in crystal properties. Comprehensiveness is the strength of the book; this allows users at different levels a choice of chapters according to their requirements.

  7. Terahertz Nanoscience of Multifunctional Materials: Atomistic Exploration

    Science.gov (United States)

    2014-03-28

    Approved for Public Release; Distribution Unlimited Final report on the project "Terahertz Nanoscience of Multifunctional Materials: Atomistic...non peer-reviewed journals: Final report on the project "Terahertz Nanoscience of Multifunctional Materials: Atomistic Exploration" Report Title In... nanoscience of multifunctional materials: atomistic exploration” PI:Inna Ponomareva We have accomplished the following. 1. We have developed a set of

  8. Atomistic Simulations of Bicelle Mixtures

    OpenAIRE

    Jiang, Yong; Wang, Hao; Kindt, James T.

    2010-01-01

    Mixtures of long- and short-tail phosphatidylcholine lipids are known to self-assemble into a variety of aggregates combining flat bilayerlike and curved micellelike features, commonly called bicelles. Atomistic simulations of bilayer ribbons and perforated bilayers containing dimyristoylphosphatidylcholine (DMPC, di-C14 tails) and dihexanoylphosphatidylcholine (DHPC, di-C6 tails) have been carried out to investigate the partitioning of these components between flat and curved microenvironmen...

  9. Fundamental ecology is fundamental.

    Science.gov (United States)

    Courchamp, Franck; Dunne, Jennifer A; Le Maho, Yvon; May, Robert M; Thébaud, Christophe; Hochberg, Michael E

    2015-01-01

    The primary reasons for conducting fundamental research are satisfying curiosity, acquiring knowledge, and achieving understanding. Here we develop why we believe it is essential to promote basic ecological research, despite increased impetus for ecologists to conduct and present their research in the light of potential applications. This includes the understanding of our environment, for intellectual, economical, social, and political reasons, and as a major source of innovation. We contend that we should focus less on short-term, objective-driven research and more on creativity and exploratory analyses, quantitatively estimate the benefits of fundamental research for society, and better explain the nature and importance of fundamental ecology to students, politicians, decision makers, and the general public. Our perspective and underlying arguments should also apply to evolutionary biology and to many of the other biological and physical sciences.

  10. Atomistic Simulations of Nanotube Fracture

    CERN Document Server

    Belytschko, T; Schatz, G; Ruoff, R S

    2002-01-01

    The fracture of carbon nanotubes is studied by atomistic simulations. The fracture behavior is found to be almost independent of the separation energy and to depend primarily on the inflection point in the interatomic potential. The rangle of fracture strians compares well with experimental results, but predicted range of fracture stresses is marketly higher than observed. Various plausible small-scale defects do not suffice to bring the failure stresses into agreement with available experimental results. As in the experiments, the fracture of carbon nanotubes is predicted to be brittle. The results show moderate dependence of fracture strength on chirality.

  11. Symmetry Breaking and Fine Structure Splitting in Zincblende Quantum Dots: Atomistic Simulations of Long-Range Strain and Piezoelectric Field

    Science.gov (United States)

    Ahmed, Shaikh; Usman, Muhammad; Heitzinger, Clemens; Rahman, Rajib; Schliwa, Andrei; Klimeck, Gerhard

    2007-04-01

    Electrons and holes captured in self-assembled quantum dots (QDs) are subject to symmetry breaking that cannot be represented in with continuum material representations. Atomistic calculations reveal symmetry lowering due to effects of strain and piezo-electric fields. These effects are fundamentally based on the crystal topology in the quantum dots. This work studies these two competing effects and demonstrates the fine structure splitting that has been demonstrated experimentally can be attributed to the underlying atomistic structure of the quantum dots.

  12. Atomistic properties of γ uranium.

    Science.gov (United States)

    Beeler, Benjamin; Deo, Chaitanya; Baskes, Michael; Okuniewski, Maria

    2012-02-22

    The properties of the body-centered cubic γ phase of uranium (U) are calculated using atomistic simulations. First, a modified embedded-atom method interatomic potential is developed for the high temperature body-centered cubic (γ) phase of U. This phase is stable only at high temperatures and is thus relatively inaccessible to first principles calculations and room temperature experiments. Using this potential, equilibrium volume and elastic constants are calculated at 0 K and found to be in close agreement with previous first principles calculations. Further, the melting point, heat capacity, enthalpy of fusion, thermal expansion and volume change upon melting are calculated and found to be in reasonable agreement with experiment. The low temperature mechanical instability of γ U is correctly predicted and investigated as a function of pressure. The mechanical instability is suppressed at pressures greater than 17.2 GPa. The vacancy formation energy is analyzed as a function of pressure and shows a linear trend, allowing for the calculation of the extrapolated zero pressure vacancy formation energy. Finally, the self-defect formation energy is analyzed as a function of temperature. This is the first atomistic calculation of γ U properties above 0 K with interatomic potentials.

  13. Fundamentally updating fundamentals.

    Science.gov (United States)

    Armstrong, Gail; Barton, Amy

    2013-01-01

    Recent educational research indicates that the six competencies of the Quality and Safety Education for Nurses initiative are best introduced in early prelicensure clinical courses. Content specific to quality and safety has traditionally been covered in senior level courses. This article illustrates an effective approach to using quality and safety as an organizing framework for any prelicensure fundamentals of nursing course. Providing prelicensure students a strong foundation in quality and safety in an introductory clinical course facilitates early adoption of quality and safety competencies as core practice values.

  14. Atomistic stimulation of defective oxides

    CERN Document Server

    Minervini, L

    2000-01-01

    defect processes. The predominant intrinsic disorder reaction and the mechanism by which excess oxygen is accommodated are established. Furthermore, the most favourable migration mechanism and pathway for oxygen ions is predicted. Chapters 7 and 8 investigate pyrochlore oxides. These materials are candidates for solid oxide fuel cell components and as actinide host phases. Such applications require a detailed understanding of the defect processes. The defect energies, displayed as contour maps, are able to account for structure stability and, given an appropriate partial charge potential model, to accurately determine the oxygen positional parameter. In particular, the dependence of the positional parameter on intrinsic disorder is predicted. It is demonstrated, by radiation damage experiments, that these results are able to predict the radiation performance of pyrochlore oxides. Atomistic simulation calculations based on energy minimization techniques and classical pair potentials are used to study several i...

  15. Local stress and heat flux in atomistic systems involving three-body forces.

    Science.gov (United States)

    Chen, Youping

    2006-02-01

    Local densities of fundamental physical quantities, including stress and heat flux fields, are formulated for atomistic systems involving three-body forces. The obtained formulas are calculable within an atomistic simulation, in consistent with the conservation equations of thermodynamics of continuum, and can be applied to systems with general two- and three-body interaction forces. It is hoped that this work may correct some misuse of inappropriate formulas of stress and heat flux in the literature, may clarify the definition of site energy of many-body potentials, and may serve as an analytical link between an atomistic model and a continuum theory. Physical meanings of the obtained formulas, their relation with virial theorem and heat theorem, and the applicability are discussed.

  16. Atomistic simulations of dislocation processes in copper

    DEFF Research Database (Denmark)

    Vegge, T.; Jacobsen, K.W.

    2002-01-01

    We discuss atomistic simulations of dislocation processes in copper based on effective medium theory interatomic potentials. Results on screw dislocation structures and processes are reviewed with particular focus on point defect mobilities and processes involving cross slip. For example, the sta......We discuss atomistic simulations of dislocation processes in copper based on effective medium theory interatomic potentials. Results on screw dislocation structures and processes are reviewed with particular focus on point defect mobilities and processes involving cross slip. For example...

  17. Atomistic Modelling of Si Nanoparticles Synthesis

    Directory of Open Access Journals (Sweden)

    Giovanni Barcaro

    2017-02-01

    Full Text Available Silicon remains the most important material for electronic technology. Presently, some efforts are focused on the use of Si nanoparticles—not only for saving material, but also for improving the efficiency of optical and electronic devices, for instance, in the case of solar cells coated with a film of Si nanoparticles. The synthesis by a bottom-up approach based on condensation from low temperature plasma is a promising technique for the massive production of such nanoparticles, but the knowledge of the basic processes occurring at the atomistic level is still very limited. In this perspective, numerical simulations can provide fundamental information of the nucleation and growth mechanisms ruling the bottom-up formation of Si nanoclusters. We propose to model the low temperature plasma by classical molecular dynamics by using the reactive force field (ReaxFF proposed by van Duin, which can properly describe bond forming and breaking. In our approach, first-principles quantum calculations are used on a set of small Si clusters in order to collect all the necessary energetic and structural information to optimize the parameters of the reactive force-field for the present application. We describe in detail the procedure used for the determination of the force field and the following molecular dynamics simulations of model systems of Si gas at temperatures in the range 2000–3000 K. The results of the dynamics provide valuable information on nucleation rate, nanoparticle size distribution, and growth rate that are the basic quantities for developing a following mesoscale model.

  18. Atomistic simulations of bicelle mixtures.

    Science.gov (United States)

    Jiang, Yong; Wang, Hao; Kindt, James T

    2010-06-16

    Mixtures of long- and short-tail phosphatidylcholine lipids are known to self-assemble into a variety of aggregates combining flat bilayerlike and curved micellelike features, commonly called bicelles. Atomistic simulations of bilayer ribbons and perforated bilayers containing dimyristoylphosphatidylcholine (DMPC, di-C(14) tails) and dihexanoylphosphatidylcholine (DHPC, di-C(6) tails) have been carried out to investigate the partitioning of these components between flat and curved microenvironments and the stabilization of the bilayer edge by DHPC. To approach equilibrium partitioning of lipids on an achievable simulation timescale, configuration-bias Monte Carlo mutation moves were used to allow individual lipids to change tail length within a semigrand-canonical ensemble. Since acceptance probabilities for direct transitions between DMPC and DHPC were negligible, a third component with intermediate tail length (didecanoylphosphatidylcholine, di-C(10) tails) was included at a low concentration to serve as an intermediate for transitions between DMPC and DHPC. Strong enrichment of DHPC is seen at ribbon and pore edges, with an excess linear density of approximately 3 nm(-1). The simulation model yields estimates for the onset of edge stability with increasing bilayer DHPC content between 5% and 15% DHPC at 300 K and between 7% and 17% DHPC at 323 K, higher than experimental estimates. Local structure and composition at points of close contact between pores suggest a possible mechanism for effective attractions between pores, providing a rationalization for the tendency of bicelle mixtures to aggregate into perforated vesicles and perforated sheets.

  19. Quantum transport in RTD and atomistic modeling of nanostructures

    Science.gov (United States)

    Jiang, Zhengping

    As devices are scaled down to nanometer scale, new materials and device structures are introduced to extend Moore's law beyond Si devices. In this length scale, carrier transport moves from classical transport to quantum transport; material granularity has more and more impacts on performance. Computer Aided Design (CAD) becomes essential for both industrial and educational purposes. First part focuses on physical models and numerical issues in nano-scale devices modeling. Resonance Tunneling Diode (RTD) is simulated and used to illustrate phenomena in carrier transport. Non-Equilibrium Green's Function (NEGF) formulism is employed in quantum transport simulation. Inhomogeneous energy grid is used in energy integration, which is critical to capture essential physics in RTD simulation. All simulation results could be reproduced by developed simulators RTDNEGF and NEMO5. In nanostructures, device length becomes comparable to material granularity; it is not proper to consider materials as continuous in many situations. Second part of this work resolves this problem by introducing atomistic modeling method. Valley degeneracy in Si (110) QW is investigated. Inconsistency of experimental observations is resolved by introducing miscut in surface. Impacts of strain and electric field on electronic bandstructure are studied. Research of SiGe barrier disorder effects on valley splitting in Si (100) QW is then conducted. Behaviors of valley splitting in different well widths under electric field are predicted by atomistic simulation. Nearest neighbor empirical tight-binding method is used in electronic calculation and VFF Keating model is used in strain relaxation.

  20. Atomistic modeling of dropwise condensation

    Science.gov (United States)

    Sikarwar, B. S.; Singh, P. L.; Muralidhar, K.; Khandekar, S.

    2016-05-01

    The basic aim of the atomistic modeling of condensation of water is to determine the size of the stable cluster and connect phenomena occurring at atomic scale to the macroscale. In this paper, a population balance model is described in terms of the rate equations to obtain the number density distribution of the resulting clusters. The residence time is taken to be large enough so that sufficient time is available for all the adatoms existing in vapor-phase to loose their latent heat and get condensed. The simulation assumes clusters of a given size to be formed from clusters of smaller sizes, but not by the disintegration of the larger clusters. The largest stable cluster size in the number density distribution is taken to be representative of the minimum drop radius formed in a dropwise condensation process. A numerical confirmation of this result against predictions based on a thermodynamic model has been obtained. Results show that the number density distribution is sensitive to the surface diffusion coefficient and the rate of vapor flux impinging on the substrate. The minimum drop radius increases with the diffusion coefficient and the impinging vapor flux; however, the dependence is weak. The minimum drop radius predicted from thermodynamic considerations matches the prediction of the cluster model, though the former does not take into account the effect of the surface properties on the nucleation phenomena. For a chemically passive surface, the diffusion coefficient and the residence time are dependent on the surface texture via the coefficient of friction. Thus, physical texturing provides a means of changing, within limits, the minimum drop radius. The study reveals that surface texturing at the scale of the minimum drop radius does not provide controllability of the macro-scale dropwise condensation at large timescales when a dynamic steady-state is reached.

  1. Atomistic computer simulations a practical guide

    CERN Document Server

    Brazdova, Veronika

    2013-01-01

    Many books explain the theory of atomistic computer simulations; this book teaches you how to run them This introductory ""how to"" title enables readers to understand, plan, run, and analyze their own independent atomistic simulations, and decide which method to use and which questions to ask in their research project. It is written in a clear and precise language, focusing on a thorough understanding of the concepts behind the equations and how these are used in the simulations. As a result, readers will learn how to design the computational model and which parameters o

  2. Atomistic Processes of Catalyst Degradation

    Energy Technology Data Exchange (ETDEWEB)

    None

    2004-11-27

    The purpose of this cooperative research and development agreement (CRADA) between Sasol North America, Inc., and the oak Ridge National Laboratory (ORNL) was to improve the stability of alumina-based industrial catalysts through the combination of aberration-corrected scanning transmission electron microscopy (STEM) at ORNL and innovative sample preparation techniques at Sasol. Outstanding progress has been made in task 1, 'Atomistic processes of La stabilization'. STEM investigations provided structural information with single-atom precision, showing the lattice location of La dopant atoms, thus enabling first-principles calculations of binding energies, which were performed in collaboration with Vanderbilt University. The stabilization mechanism turns out to be entirely due to a particularly strong binding energy of the La tom to the {gamma}-alumina surface. The large size of the La atom precludes incorporation of La into the bulk alumina and also strains the surface, thus preventing any clustering of La atoms. Thus highly disperse distribution is achieved and confirmed by STEM images. la also affects relative stability of the exposed surfaces of {gamma}-alumina, making the 100 surface more stable for the doped case, unlike the 110 surface for pure {gamma}-alumina. From the first-principles calculations, they can estimate the increase in transition temperature for the 3% loading of La used commercially, and it is in excellent agreement with experiment. This task was further pursued aiming to generate useable recommendations for the optimization of the preparation techniques for La-doped aluminas. The effort was primarily concentrated on the connection between the boehmitre-{gamma}-Al{sub 2}O{sub 3} phase transition (i.e. catalyst preparation) and the resulting dispersion of La on the {gamma}-Al{sub 2}O{sub 3} surface. It was determined that the La distribution on boehmite was non-uniform and different from that on the {gamma}-Al{sub 2}O{sub 3} and thus

  3. Quantum-based Atomistic Simulation of Transition Metals

    Energy Technology Data Exchange (ETDEWEB)

    Moriarty, J A; Benedict, L X; Glosli, J N; Hood, R Q; Orlikowski, D A; Patel, M V; Soderlind, P; Streitz, F H; Tang, M; Yang, L H

    2005-08-29

    First-principles generalized pseudopotential theory (GPT) provides a fundamental basis for transferable multi-ion interatomic potentials in d-electron transition metals within density-functional quantum mechanics. In mid-period bcc metals, where multi-ion angular forces are important to structural properties, simplified model GPT or MGPT potentials have been developed based on canonical d bands to allow analytic forms and large-scale atomistic simulations. Robust, advanced-generation MGPT potentials have now been obtained for Ta and Mo and successfully applied to a wide range of structural, thermodynamic, defect and mechanical properties at both ambient and extreme conditions of pressure and temperature. Recent algorithm improvements have also led to a more general matrix representation of MGPT beyond canonical bands allowing increased accuracy and extension to f-electron actinide metals, an order of magnitude increase in computational speed, and the current development of temperature-dependent potentials.

  4. Fundamentals of fluid lubrication

    Science.gov (United States)

    Hamrock, Bernard J.

    1991-01-01

    The aim is to coordinate the topics of design, engineering dynamics, and fluid dynamics in order to aid researchers in the area of fluid film lubrication. The lubrication principles that are covered can serve as a basis for the engineering design of machine elements. The fundamentals of fluid film lubrication are presented clearly so that students that use the book will have confidence in their ability to apply these principles to a wide range of lubrication situations. Some guidance on applying these fundamentals to the solution of engineering problems is also provided.

  5. Fundamentals of piping design

    CERN Document Server

    Smith, Peter

    2013-01-01

    Written for the piping engineer and designer in the field, this two-part series helps to fill a void in piping literature,since the Rip Weaver books of the '90s were taken out of print at the advent of the Computer Aid Design(CAD) era. Technology may have changed, however the fundamentals of piping rules still apply in the digitalrepresentation of process piping systems. The Fundamentals of Piping Design is an introduction to the designof piping systems, various processes and the layout of pipe work connecting the major items of equipment forthe new hire, the engineering student and the vetera

  6. Systematic study of grain boundary atomistic structures and related properties in cubic zirconia bicrystals

    Energy Technology Data Exchange (ETDEWEB)

    Shibata, N.; Ikuhara, Y. [Inst. of Engineering Innovation, Univ. of Tokyo, Tokyo (Japan); Oba, F. [Dept. of Materials Science and Engineering, Graduate School of Engineering, Kyoto Univ., Kyoto (Japan); Yamamoto, T. [Dept. of Advanced Materials Science, Graduate School of Frontier Science, Univ. of Tokyo, Kashiwa, Chiba (Japan)

    2005-02-01

    Systematic grain boundary study of cubic zirconia has been conducted by using bicrystals. It is clearly demonstrated that grain boundary atomistic structures dramatically change according to the misorientations and plane orientations of the boundaries, resulting in a dramatic change of excess energies and solute segregation behaviors. Combining with theoretical calculations, it is found that grain boundaries possess unique coordination-deficient cation sites at the cores, and their densities have a clear correlation with these properties in high-angle grain boundaries. This result indicates that grain boundary properties in ceramics are possibly determined by the accumulation of coordination-deficient sites. Thus, systematic grain boundary study using bicrystal offers fundamental understandings of the relationship between atomistic structures and properties in ceramic grain boundaries. (orig.)

  7. Radiology fundamentals

    CERN Document Server

    Singh, Harjit

    2011-01-01

    ""Radiology Fundamentals"" is a concise introduction to the dynamic field of radiology for medical students, non-radiology house staff, physician assistants, nurse practitioners, radiology assistants, and other allied health professionals. The goal of the book is to provide readers with general examples and brief discussions of basic radiographic principles and to serve as a curriculum guide, supplementing a radiology education and providing a solid foundation for further learning. Introductory chapters provide readers with the fundamental scientific concepts underlying the medical use of imag

  8. Fundamental enabling issues in nanotechnology :

    Energy Technology Data Exchange (ETDEWEB)

    Floro, Jerrold Anthony [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Foiles, Stephen Martin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hearne, Sean Joseph [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hoyt, Jeffrey John [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Seel, Steven Craig [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Webb III, Edmund Blackburn [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Morales, Alfredo Martin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Zimmerman, Jonathan A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2007-10-01

    To effectively integrate nanotechnology into functional devices, fundamental aspects of material behavior at the nanometer scale must be understood. Stresses generated during thin film growth strongly influence component lifetime and performance; stress has also been proposed as a mechanism for stabilizing supported nanoscale structures. Yet the intrinsic connections between the evolving morphology of supported nanostructures and stress generation are still a matter of debate. This report presents results from a combined experiment and modeling approach to study stress evolution during thin film growth. Fully atomistic simulations are presented predicting stress generation mechanisms and magnitudes during all growth stages, from island nucleation to coalescence and film thickening. Simulations are validated by electrodeposition growth experiments, which establish the dependence of microstructure and growth stresses on process conditions and deposition geometry. Sandia is one of the few facilities with the resources to combine experiments and modeling/theory in this close a fashion. Experiments predicted an ongoing coalescence process that generates signficant tensile stress. Data from deposition experiments also supports the existence of a kinetically limited compressive stress generation mechanism. Atomistic simulations explored island coalescence and deposition onto surfaces intersected by grain boundary structures to permit investigation of stress evolution during later growth stages, e.g. continual island coalescence and adatom incorporation into grain boundaries. The predictive capabilities of simulation permit direct determination of fundamental processes active in stress generation at the nanometer scale while connecting those processes, via new theory, to continuum models for much larger island and film structures. Our combined experiment and simulation results reveal the necessary materials science to tailor stress, and therefore performance, in

  9. Fundamental Astronomy

    CERN Document Server

    Karttunen, Hannu; Oja, Heikki; Poutanen, Markku; Donner, Karl Johan

    2007-01-01

    Fundamental Astronomy gives a well-balanced and comprehensive introduction to the topics of classical and modern astronomy. While emphasizing both the astronomical concepts and the underlying physical principles, the text provides a sound basis for more profound studies in the astronomical sciences. The fifth edition of this successful undergraduate textbook has been extensively modernized and extended in the parts dealing with the Milky Way, extragalactic astronomy and cosmology as well as with extrasolar planets and the solar system (as a consequence of recent results from satellite missions and the new definition by the International Astronomical Union of planets, dwarf planets and small solar-system bodies). Furthermore a new chapter on astrobiology has been added. Long considered a standard text for physical science majors, Fundamental Astronomy is also an excellent reference and entrée for dedicated amateur astronomers.

  10. Atomistic deformation mechanisms in twinned copper nanospheres.

    Science.gov (United States)

    Bian, Jianjun; Niu, Xinrui; Zhang, Hao; Wang, Gangfeng

    2014-01-01

    In the present study, we perform molecular dynamic simulations to investigate the compression response and atomistic deformation mechanisms of twinned nanospheres. The relationship between load and compression depth is calculated for various twin spacing and loading directions. Then, the overall elastic properties and the underlying plastic deformation mechanisms are illuminated. Twin boundaries (TBs) act as obstacles to dislocation motion and lead to strengthening. As the loading direction varies, the plastic deformation transfers from dislocations intersecting with TBs, slipping parallel to TBs, and then to being restrained by TBs. The strengthening of TBs depends strongly on the twin spacing.

  11. Atomistic Mechanisms of Fatigue in Nanocrystalline Metals

    Science.gov (United States)

    Farkas, D.; Willemann, M.; Hyde, B.

    2005-04-01

    We investigate the mechanisms of fatigue behavior in nanocrystalline metals at the atomic scale using empirical force laws and molecular level simulations. A combination of molecular statics and molecular dynamics was used to deal with the time scale limitations of molecular dynamics. We show that the main atomistic mechanism of fatigue crack propagation in these materials is the formation of nanovoids ahead of the main crack. The results obtained for crack advance as a function of stress intensity amplitude are consistent with experimental studies and a Paris law exponent of about 2.

  12. Physically representative atomistic modeling of atomic-scale friction

    Science.gov (United States)

    Dong, Yalin

    Nanotribology is a research field to study friction, adhesion, wear and lubrication occurred between two sliding interfaces at nano scale. This study is motivated by the demanding need of miniaturization mechanical components in Micro Electro Mechanical Systems (MEMS), improvement of durability in magnetic storage system, and other industrial applications. Overcoming tribological failure and finding ways to control friction at small scale have become keys to commercialize MEMS with sliding components as well as to stimulate the technological innovation associated with the development of MEMS. In addition to the industrial applications, such research is also scientifically fascinating because it opens a door to understand macroscopic friction from the most bottom atomic level, and therefore serves as a bridge between science and engineering. This thesis focuses on solid/solid atomic friction and its associated energy dissipation through theoretical analysis, atomistic simulation, transition state theory, and close collaboration with experimentalists. Reduced-order models have many advantages for its simplification and capacity to simulating long-time event. We will apply Prandtl-Tomlinson models and their extensions to interpret dry atomic-scale friction. We begin with the fundamental equations and build on them step-by-step from the simple quasistatic one-spring, one-mass model for predicting transitions between friction regimes to the two-dimensional and multi-atom models for describing the effect of contact area. Theoretical analysis, numerical implementation, and predicted physical phenomena are all discussed. In the process, we demonstrate the significant potential for this approach to yield new fundamental understanding of atomic-scale friction. Atomistic modeling can never be overemphasized in the investigation of atomic friction, in which each single atom could play a significant role, but is hard to be captured experimentally. In atomic friction, the

  13. Electronic circuits fundamentals & applications

    CERN Document Server

    Tooley, Mike

    2015-01-01

    Electronics explained in one volume, using both theoretical and practical applications.New chapter on Raspberry PiCompanion website contains free electronic tools to aid learning for students and a question bank for lecturersPractical investigations and questions within each chapter help reinforce learning Mike Tooley provides all the information required to get to grips with the fundamentals of electronics, detailing the underpinning knowledge necessary to appreciate the operation of a wide range of electronic circuits, including amplifiers, logic circuits, power supplies and oscillators. The

  14. Marketing fundamentals.

    Science.gov (United States)

    Redmond, W H

    2001-01-01

    This chapter outlines current marketing practice from a managerial perspective. The role of marketing within an organization is discussed in relation to efficiency and adaptation to changing environments. Fundamental terms and concepts are presented in an applied context. The implementation of marketing plans is organized around the four P's of marketing: product (or service), promotion (including advertising), place of delivery, and pricing. These are the tools with which marketers seek to better serve their clients and form the basis for competing with other organizations. Basic concepts of strategic relationship management are outlined. Lastly, alternate viewpoints on the role of advertising in healthcare markets are examined.

  15. Bridging Atomistic/Continuum Scales in Solids with Moving Dislocations

    Institute of Scientific and Technical Information of China (English)

    TANG Shao-Qiang; LIU Wing K.; KARPOV Eduard G.; HOU Thomas Y.

    2007-01-01

    @@ We propose a multiscale method for simulating solids with moving dislocations. Away from atomistic subdomains where the atomistic dynamics are fully resolved, a dislocation is represented by a localized jump profile, superposed on a defect-free field. We assign a thin relay zone around an atomistic subdomain to detect the dislocation profile and its propagation speed at a selected relay time. The detection technique utilizes a lattice time history integral treatment. After the relay, an atomistic computation is performed only for the defect-free field. The method allows one to effectively absorb the fine scale fluctuations and the dynamic dislocations at the interface between the atomistic and continuum domains. In the surrounding region, a coarse grid computation is adequate.

  16. Atomistic simulations of nanoscale electrokinetic transport

    Science.gov (United States)

    Liu, Jin; Wang, Moran; Chen, Shiyi; Robbins, Mark

    2011-11-01

    An efficient and accurate algorithm for atomistic simulations of nanoscale electrokinetic transport will be described. The long-range interactions between charged molecules are treated using the Particle-Particle Particle-Mesh method and the Poisson equation for the electric potential is solved using an efficient multi-grid method in physical space. Using this method, we investigate two important applications in electrokinetic transport: electroosmotic flow in rough channels and electowetting on dielectric (EWOD). Simulations of electroosmotic and pressure driven flow in exactly the same geometries show that surface roughness has a much more pronounced effect on electroosmotic flow. Analysis of local quantities shows that this is because the driving force in electroosmotic flow is localized near the wall where the charge density is high. In atomistic simulations of EWOD, we find the contact angle follows the continuum theory at low voltages and always saturates at high voltages. Based on our results, a new mechanism for saturation is identified and possible techniques for controlling saturation are proposed. This work is supported by the National Science Foundation under Grant No. CMMI 0709187.

  17. Atomistic Monte Carlo Simulation of Lipid Membranes

    Directory of Open Access Journals (Sweden)

    Daniel Wüstner

    2014-01-01

    Full Text Available Biological membranes are complex assemblies of many different molecules of which analysis demands a variety of experimental and computational approaches. In this article, we explain challenges and advantages of atomistic Monte Carlo (MC simulation of lipid membranes. We provide an introduction into the various move sets that are implemented in current MC methods for efficient conformational sampling of lipids and other molecules. In the second part, we demonstrate for a concrete example, how an atomistic local-move set can be implemented for MC simulations of phospholipid monomers and bilayer patches. We use our recently devised chain breakage/closure (CBC local move set in the bond-/torsion angle space with the constant-bond-length approximation (CBLA for the phospholipid dipalmitoylphosphatidylcholine (DPPC. We demonstrate rapid conformational equilibration for a single DPPC molecule, as assessed by calculation of molecular energies and entropies. We also show transition from a crystalline-like to a fluid DPPC bilayer by the CBC local-move MC method, as indicated by the electron density profile, head group orientation, area per lipid, and whole-lipid displacements. We discuss the potential of local-move MC methods in combination with molecular dynamics simulations, for example, for studying multi-component lipid membranes containing cholesterol.

  18. Multiscale Modeling of Grain-Boundary Fracture: Cohesive Zone Models Parameterized From Atomistic Simulations

    Science.gov (United States)

    Glaessgen, Edward H.; Saether, Erik; Phillips, Dawn R.; Yamakov, Vesselin

    2006-01-01

    A multiscale modeling strategy is developed to study grain boundary fracture in polycrystalline aluminum. Atomistic simulation is used to model fundamental nanoscale deformation and fracture mechanisms and to develop a constitutive relationship for separation along a grain boundary interface. The nanoscale constitutive relationship is then parameterized within a cohesive zone model to represent variations in grain boundary properties. These variations arise from the presence of vacancies, intersticies, and other defects in addition to deviations in grain boundary angle from the baseline configuration considered in the molecular dynamics simulation. The parameterized cohesive zone models are then used to model grain boundaries within finite element analyses of aluminum polycrystals.

  19. AGU Chapman Conference Hydrogeologic Processes: Building and Testing Atomistic- to Basin-Scale Models

    Energy Technology Data Exchange (ETDEWEB)

    Weaver, B. [American Geophysical Union, Washington, DC (United States)

    1994-12-31

    This report presents details of the Chapman Conference given on June 6--9, 1994 in Lincoln, New Hampshire. This conference covered the scale of processes involved in coupled hydrogeologic mass transport and a concept of modeling and testing from the atomistic- to the basin- scale. Other topics include; the testing of fundamental atomic level parameterizations in the laboratory and field studies of fluid flow and mass transport and the next generation of hydrogeologic models. Individual papers from this conference are processed separately for the database.

  20. Scalable Atomistic Simulation Algorithms for Materials Research

    Directory of Open Access Journals (Sweden)

    Aiichiro Nakano

    2002-01-01

    Full Text Available A suite of scalable atomistic simulation programs has been developed for materials research based on space-time multiresolution algorithms. Design and analysis of parallel algorithms are presented for molecular dynamics (MD simulations and quantum-mechanical (QM calculations based on the density functional theory. Performance tests have been carried out on 1,088-processor Cray T3E and 1,280-processor IBM SP3 computers. The linear-scaling algorithms have enabled 6.44-billion-atom MD and 111,000-atom QM calculations on 1,024 SP3 processors with parallel efficiency well over 90%. production-quality programs also feature wavelet-based computational-space decomposition for adaptive load balancing, spacefilling-curve-based adaptive data compression with user-defined error bound for scalable I/O, and octree-based fast visibility culling for immersive and interactive visualization of massive simulation data.

  1. Atomistic Monte Carlo simulation of lipid membranes

    DEFF Research Database (Denmark)

    Wüstner, Daniel; Sklenar, Heinz

    2014-01-01

    Biological membranes are complex assemblies of many different molecules of which analysis demands a variety of experimental and computational approaches. In this article, we explain challenges and advantages of atomistic Monte Carlo (MC) simulation of lipid membranes. We provide an introduction......, as assessed by calculation of molecular energies and entropies. We also show transition from a crystalline-like to a fluid DPPC bilayer by the CBC local-move MC method, as indicated by the electron density profile, head group orientation, area per lipid, and whole-lipid displacements. We discuss the potential...... of local-move MC methods in combination with molecular dynamics simulations, for example, for studying multi-component lipid membranes containing cholesterol....

  2. Towards Automated Benchmarking of Atomistic Forcefields: Neat Liquid Densities and Static Dielectric Constants from the ThermoML Data Archive

    CERN Document Server

    Beauchamp, Kyle A; Rustenburg, Ariën S; Bayly, Christopher I; Kroenlein, Kenneth; Chodera, John D

    2015-01-01

    Atomistic molecular simulations are a powerful way to make quantitative predictions, but the accuracy of these predictions depends entirely on the quality of the forcefield employed. While experimental measurements of fundamental physical properties offer a straightforward approach for evaluating forcefield quality, the bulk of this information has been tied up in formats that are not machine-readable. Compiling benchmark datasets of physical properties from non-machine-readable sources require substantial human effort and is prone to accumulation of human errors, hindering the development of reproducible benchmarks of forcefield accuracy. Here, we examine the feasibility of benchmarking atomistic forcefields against the NIST ThermoML data archive of physicochemical measurements, which aggregates thousands of experimental measurements in a portable, machine-readable, self-annotating format. As a proof of concept, we present a detailed benchmark of the generalized Amber small molecule forcefield (GAFF) using t...

  3. NiTi superelasticity via atomistic simulations

    Science.gov (United States)

    Chowdhury, Piyas; Ren, Guowu; Sehitoglu, Huseyin

    2015-12-01

    The NiTi shape memory alloys (SMAs) are promising candidates for the next-generation multifunctional materials. These materials are superelastic i.e. they can fully recover their original shape even after fairly large inelastic deformations once the mechanical forces are removed. The superelasticity reportedly stems from atomic scale crystal transformations. However, very few computer simulations have emerged, elucidating the transformation mechanisms at the discrete lattice level, which underlie the extraordinary strain recoverability. Here, we conduct breakthrough molecular dynamics modelling on the superelastic behaviour of the NiTi single crystals, and unravel the atomistic genesis thereof. The deformation recovery is clearly traced to the reversible transformation between austenite and martensite crystals through simulations. We examine the mechanistic origin of the tension-compression asymmetries and the effects of pressure/temperature/strain rate variation isolatedly. Hence, this work essentially brings a new dimension to probing the NiTi performance based on the mesoscale physics under more complicated thermo-mechanical loading scenarios.

  4. Strain Functionals for Characterizing Atomistic Geometries

    Science.gov (United States)

    Kober, Edward; Rudin, Sven

    The development of a set of strain tensor functionals that are capable of characterizing arbitrarily ordered atomistic structures is described. This approach defines a Gaussian-weighted neighborhood around each atom and characterizes that local geometry in terms of n-th order strain tensors, which are equivalent to the moments of the neighborhood. Fourth order expansions can distinguish the cubic structures (and deformations thereof), but sixth order expansions are required to fully characterize hexagonal structures. Other methods used to characterize atomic structures, such as the Steinhardt parameters or the centrosymmetry metric, can be derived from this more general approach. These functions are continuous and smooth and much less sensitive to thermal fluctuations than other descriptors based on discrete neighborhoods. They allow material phases, deformations, and a large number of defect structures to be readily identified and classified. Applications to the analysis of shock-loaded samples of Cu, Ta and Ti will be presented. This strain functional basis can also then be used for developing interatomic potential functions, and an initial application to Cu will be presented.

  5. Stress in titania nanoparticles: An atomistic study

    Energy Technology Data Exchange (ETDEWEB)

    Darkins, Robert; Sushko, Maria L.; Liu, Jun; Duffy, Dorothy M.

    2014-04-24

    Stress engineering is becoming an increasingly important method for controlling electronic, optical, and magnetic properties of nanostructures, although the concept of stress is poorly defined at the nanoscale. We outline a methodology for computing bulk and surface stress in nanoparticles using atomistic simulation. The method is applicable to ionic and non- ionic materials alike and may be extended to other nanostructures. We apply it to spherical anatase nanoparticles ranging from 2 to 6 nm in diameter and obtain a surface stress of 0.89 N/m, in agreement with experimental measurements. Based on the extent that stress inhomogeneities at the surface are transmitted into the bulk, two characteristic length-scales are identified: below 3 nm bulk and surface regions cannot be defined and the available analytic theories for stress are not applicable, and above about 5 nm the stress becomes well-described by the theoretical Young-Laplace equation. The effect of a net surface charge on the bulk stress is also investigated. It is found that moderate surface charges can induce significant bulk stresses, on the order of 100 MPa, in nanoparticles within this size range.

  6. Atomistic simulation of Voronoi-based coated nanoporous metals

    Science.gov (United States)

    Onur Yildiz, Yunus; Kirca, Mesut

    2017-02-01

    In this study, a new method developed for the generation of periodic atomistic models of coated and uncoated nanoporous metals (NPMs) is presented by examining the thermodynamic stability of coated nanoporous structures. The proposed method is mainly based on the Voronoi tessellation technique, which provides the ability to control cross-sectional dimension and slenderness of ligaments as well as the thickness of coating. By the utilization of the method, molecular dynamic (MD) simulations of randomly structured NPMs with coating can be performed efficiently in order to investigate their physical characteristics. In this context, for the purpose of demonstrating the functionality of the method, sample atomistic models of Au/Pt NPMs are generated and the effects of coating and porosity on the thermodynamic stability are investigated by using MD simulations. In addition to that, uniaxial tensile loading simulations are performed via MD technique to validate the nanoporous models by comparing the effective Young’s modulus values with the results from literature. Based on the results, while it is demonstrated that coating the nanoporous structures slightly decreases the structural stability causing atomistic configurational changes, it is also shown that the stability of the atomistic models is higher at lower porosities. Furthermore, adaptive common neighbour analysis is also performed to identify the stabilized atomistic structure after the coating process, which provides direct foresights for the mechanical behaviour of coated nanoporous structures.

  7. A robust, coupled approach for atomistic-continuum simulation.

    Energy Technology Data Exchange (ETDEWEB)

    Aubry, Sylvie; Webb, Edmund Blackburn, III (Sandia National Laboratories, Albuquerque, NM); Wagner, Gregory John; Klein, Patrick A.; Jones, Reese E.; Zimmerman, Jonathan A.; Bammann, Douglas J.; Hoyt, Jeffrey John (Sandia National Laboratories, Albuquerque, NM); Kimmer, Christopher J.

    2004-09-01

    This report is a collection of documents written by the group members of the Engineering Sciences Research Foundation (ESRF), Laboratory Directed Research and Development (LDRD) project titled 'A Robust, Coupled Approach to Atomistic-Continuum Simulation'. Presented in this document is the development of a formulation for performing quasistatic, coupled, atomistic-continuum simulation that includes cross terms in the equilibrium equations that arise due to kinematic coupling and corrections used for the calculation of system potential energy to account for continuum elements that overlap regions containing atomic bonds, evaluations of thermo-mechanical continuum quantities calculated within atomistic simulations including measures of stress, temperature and heat flux, calculation used to determine the appropriate spatial and time averaging necessary to enable these atomistically-defined expressions to have the same physical meaning as their continuum counterparts, and a formulation to quantify a continuum 'temperature field', the first step towards constructing a coupled atomistic-continuum approach capable of finite temperature and dynamic analyses.

  8. Hybrid continuum-atomistic approach to model electrokinetics in nanofluidics

    Energy Technology Data Exchange (ETDEWEB)

    Amani, Ehsan, E-mail: eamani@aut.ac.ir; Movahed, Saeid, E-mail: smovahed@aut.ac.ir

    2016-06-07

    In this study, for the first time, a hybrid continuum-atomistic based model is proposed for electrokinetics, electroosmosis and electrophoresis, through nanochannels. Although continuum based methods are accurate enough to model fluid flow and electric potential in nanofluidics (in dimensions larger than 4 nm), ionic concentration is too low in nanochannels for the continuum assumption to be valid. On the other hand, the non-continuum based approaches are too time-consuming and therefore is limited to simple geometries, in practice. Here, to propose an efficient hybrid continuum-atomistic method of modelling the electrokinetics in nanochannels; the fluid flow and electric potential are computed based on continuum hypothesis coupled with an atomistic Lagrangian approach for the ionic transport. The results of the model are compared to and validated by the results of the molecular dynamics technique for a couple of case studies. Then, the influences of bulk ionic concentration, external electric field, size of nanochannel, and surface electric charge on the electrokinetic flow and ionic mass transfer are investigated, carefully. The hybrid continuum-atomistic method is a promising approach to model more complicated geometries and investigate more details of the electrokinetics in nanofluidics. - Highlights: • A hybrid continuum-atomistic model is proposed for electrokinetics in nanochannels. • The model is validated by molecular dynamics. • This is a promising approach to model more complicated geometries and physics.

  9. An object oriented Python interface for atomistic simulations

    Science.gov (United States)

    Hynninen, T.; Himanen, L.; Parkkinen, V.; Musso, T.; Corander, J.; Foster, A. S.

    2016-01-01

    Programmable simulation environments allow one to monitor and control calculations efficiently and automatically before, during, and after runtime. Environments directly accessible in a programming environment can be interfaced with powerful external analysis tools and extensions to enhance the functionality of the core program, and by incorporating a flexible object based structure, the environments make building and analysing computational setups intuitive. In this work, we present a classical atomistic force field with an interface written in Python language. The program is an extension for an existing object based atomistic simulation environment.

  10. Atomistic Simulation of Non-Equilibrium Phenomena in Hypersonic Flows

    Science.gov (United States)

    Norman, Paul Erik

    The goal of this work is to model the heterogeneous recombination of atomic oxygen on silica surfaces, which is of interest for accurately predicting the heating on vehicles traveling at hypersonic speeds. This is accomplished by creating a finite rate catalytic model, which describes recombination with a set of elementary gas-surface reactions. Fundamental to a description of surface catalytic reactions are the in situ chemical structures on the surface where recombination can occur. Using molecular dynamics simulations with the Reax GSISiO potential, we find that the chemical sites active in direct gas-phase reactions on silica surfaces consist of a small number of specific structures (or defects). The existence of these defects on real silica surfaces is supported by experimental results and the structure and energetics of these defects have been verified with quantum chemical calculations. The reactions in the finite rate catalytic model are based on the interaction of molecular and atomic oxygen with these defects. Trajectory calculations are used to find the parameters in the forward rate equations, while a combination of detailed balance and transition state theory are used to find the parameters in the reverse rate equations. The rate model predicts that the oxygen recombination coefficient is relatively constant at T (300-1000 K), in agreement with experimental results. At T > 1000 K the rate model predicts a drop off in the oxygen recombination coefficient, in disagreement with experimental results, which predict that the oxygen recombination coefficient increases with temperature. A discussion of the possible reasons for this disagreement, including non-adiabatic collision dynamics, variable surface site concentrations, and additional recombination mechanisms is presented. This thesis also describes atomistic simulations with Classical Trajectory Calculation Direction Simulation Monte Carlo (CTC-DSMC), a particle based method for modeling non

  11. Predictive atomistic simulations of electronic properties of realistic nanoscale devices: A multiscale modeling approach

    Science.gov (United States)

    Vedula, Ravi Pramod Kumar

    Scaling of CMOS towards its ultimate limits, where quantum effects and atomistic variability due to fabrication, along with recent emphasis on heterogeneous integration of non-digital devices for increasing the functional diversification presents us with fundamentally new challenges. A comprehensive understanding of design and operation of these nanoscale transistors, and other electronic devices like RF-MEMS, requires an insight into their electronic and mechanical properties that are strongly influenced by underlying atomic structure. Hence, continuum descriptions of materials and use of empirical models at these scales become questionable. This increase in complexity of electronic devices necessitates an understanding at a more fundamental level to accurately predict the performance and reliability of these devices. The objective of this thesis is to outline the application of multiscale predictive modeling methods, ranging from atoms to devices, for addressing these challenges. This capability is demonstrated using two examples: characterization of (i) dielectric charging in RF-MEMS, and (ii) transport properties of Ge-nanofins. For characterizing the dielectric charging phenomenon, a continuum dielectric charging model, augmented by first principles informed trap distributions, is used to predict current transient measurements across a broad range of voltages and temperatures. These simulations demonstrate using ab initio informed model not only reduces the empiricism (number of adjustable parameters) in the model but also leads to a more accurate model over a broad range of operating conditions, and enable the precise determination of additional material parameters. These atomistic calculations also provide detailed information about the nature of charge traps and their trapping mechanisms that are not accessible experimentally; such information could prove invaluable in defect engineering. The second problem addresses the effect of the in-homogeneous strain

  12. Definition and detection of contact in atomistic simulations

    NARCIS (Netherlands)

    Solhjoo, Soheil; Vakis, Antonis I.

    2015-01-01

    In atomistic simulations, contact depends on the accurate detection of contacting atoms as well as their contact area. While it is common to define contact between atoms based on the so-called ‘contact distance’ where the interatomic potential energy reaches its minimum, this discounts, for example,

  13. Adaptive resolution simulation of an atomistic protein in MARTINI water

    NARCIS (Netherlands)

    Zavadlav, Julija; Melo, Manuel Nuno; Marrink, Siewert J.; Praprotnik, Matej

    2014-01-01

    We present an adaptive resolution simulation of protein G in multiscale water. We couple atomistic water around the protein with mesoscopic water, where four water molecules are represented with one coarse-grained bead, farther away. We circumvent the difficulties that arise from coupling to the coa

  14. Atomistic Determination of Cross-Slip Pathway and Energetics

    DEFF Research Database (Denmark)

    Rasmussen, Torben; Jacobsen, Karsten Wedel; Leffers, Torben;

    1997-01-01

    The mechanism for cross slip of a screw dislocation in Cu is determined by atomistic simulations that only presume the initial and final states of the process. The dissociated dislocation constricts in the primary plane and redissociates into the cross-slip plane while still partly in the primary...

  15. Atomistic simulations of jog migration on extended screw dislocations

    DEFF Research Database (Denmark)

    Vegge, T.; Leffers, T.; Pedersen, O.B.;

    2001-01-01

    We have performed large-scale atomistic simulations of the migration of elementary jogs on dissociated screw dislocations in Cu. The local crystalline configurations, transition paths. effective masses. and migration barriers for the jogs are determined using an interatomic potential based on the...

  16. Hearing Aids

    Science.gov (United States)

    ... more in both quiet and noisy situations. Hearing aids help people who have hearing loss from damage ... your doctor. There are different kinds of hearing aids. They differ by size, their placement on or ...

  17. AIDS (image)

    Science.gov (United States)

    AIDS (acquired immune deficiency syndrome) is caused by HIV (human immunodeficiency virus), and is a syndrome that ... life-threatening illnesses. There is no cure for AIDS, but treatment with antiviral medicine can suppress symptoms. ...

  18. Aid Effectiveness

    DEFF Research Database (Denmark)

    Arndt, Channing; Jones, Edward Samuel; Tarp, Finn

    Controversy over the aggregate impact of foreign aid has focused on reduced form estimates of the aid-growth link. The causal chain, through which aid affects developmental outcomes including growth, has received much less attention. We address this gap by: (i) specifying a structural model of th...

  19. Adhesive contact:from atomistic model to continuum model

    Institute of Scientific and Technical Information of China (English)

    Fan Kang-Qi; Jia Jian-Yuan; Zhu Ying-Min; Zhang Xiu-Yan

    2011-01-01

    Two types of Lennard-Jones potential are widely used in modeling adhesive contacts. However, the relationships between the parameters of the two types of Lennard-Jones potential are not well defined. This paper employs a selfconsistent method to derive the Lennard-Jones surface force law from the interatomic Lennard-Jones potential with emphasis on the relationships between the parameters. The effect of using correct parameters in the adhesion models is demonstrated in single sphere-flat contact via continuum models and an atomistic model. Furthermore, the adhesion hysteresis behaviour is investigated, and the S-shaped force-distance relation is revealed by the atomistic model. It shows that the adhesion hysteresis loop is generated by the jump-to-contact and jump-off-contact, which are illustrated by the S-shaped force-distance curve.

  20. Atomistic aspects of crack propagation along high angle grain boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, D. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering

    1997-12-31

    The author presents atomistic simulations of the crack tip configuration near a high angle {Sigma} = 5 [001](210) symmetrical tilt grain boundary in NiAl. The simulations were carried out using molecular statics and embedded atom (EAM) potentials. The cracks are stabilized near a Griffith condition involving the cohesive energy of the grain boundary. The atomistic configurations of the tip region are different in the presence of the high angle grain boundary than in the bulk. Three different configurations of the grain boundary were studied corresponding to different local compositions. It was found that in ordered NiAl, cracks along symmetrical tilt boundaries show a more brittle behavior for Al rich boundaries than for Ni-rich boundaries. Lattice trapping effects in grain boundary fracture were found to be more significant than in the bulk.

  1. The notion of a plastic material spin in atomistic simulations

    Science.gov (United States)

    Dickel, D.; Tenev, T. G.; Gullett, P.; Horstemeyer, M. F.

    2016-12-01

    A kinematic algorithm is proposed to extend existing constructions of strain tensors from atomistic data to decouple elastic and plastic contributions to the strain. Elastic and plastic deformation and ultimately the plastic spin, useful quantities in continuum mechanics and finite element simulations, are computed from the full, discrete deformation gradient and an algorithm for the local elastic deformation gradient. This elastic deformation gradient algorithm identifies a crystal type using bond angle analysis (Ackland and Jones 2006 Phys. Rev. B 73 054104) and further exploits the relationship between bond angles to determine the local deformation from an ideal crystal lattice. Full definitions of plastic deformation follow directly using a multiplicative decomposition of the deformation gradient. The results of molecular dynamics simulations of copper in simple shear and torsion are presented to demonstrate the ability of these new discrete measures to describe plastic material spin in atomistic simulation and to compare them with continuum theory.

  2. Atomistic modeling of carbon Cottrell atmospheres in bcc iron

    Science.gov (United States)

    Veiga, R. G. A.; Perez, M.; Becquart, C. S.; Domain, C.

    2013-01-01

    Atomistic simulations with an EAM interatomic potential were used to evaluate carbon-dislocation binding energies in bcc iron. These binding energies were then used to calculate the occupation probability of interstitial sites in the vicinity of an edge and a screw dislocation. The saturation concentration due to carbon-carbon interactions was also estimated by atomistic simulations in the dislocation core and taken as an upper limit for carbon concentration in a Cottrell atmosphere. We obtained a maximum concentration of 10 ± 1 at.% C at T = 0 K within a radius of 1 nm from the dislocation lines. The spatial carbon distributions around the line defects revealed that the Cottrell atmosphere associated with an edge dislocation is denser than that around a screw dislocation, in contrast with the predictions of the classical model of Cochardt and colleagues. Moreover, the present Cottrell atmosphere model is in reasonable quantitative accord with the three-dimensional atom probe data available in the literature.

  3. Predicting dislocation climb: Classical modeling versus atomistic simulations

    OpenAIRE

    Clouet, Emmanuel

    2011-01-01

    International audience; The classical modeling of dislocation climb based on a continuous description of vacancy diffusion is compared to recent atomistic simulations of dislocation climb in body-centered cubic iron under vacancy supersaturation [Phys. Rev. Lett. 105 095501 (2010)]. A quantitative agreement is obtained, showing the ability of the classical approach to describe dislocation climb. The analytical model is then used to extrapolate dislocation climb velocities to lower dislocation...

  4. Redox reactions with empirical potentials: Atomistic battery discharge simulations

    OpenAIRE

    Dapp, Wolf B.; Müser, Martin H.

    2013-01-01

    Batteries are pivotal components in overcoming some of today's greatest technological challenges. Yet to date there is no self-consistent atomistic description of a complete battery. We take first steps toward modeling of a battery as a whole microscopically. Our focus lies on phenomena occurring at the electrode-electrolyte interface which are not easily studied with other methods. We use the redox split-charge equilibration (redoxSQE) method that assigns a discrete ionization state to each ...

  5. The atomistic representation of first strain-gradient elastic tensors

    Science.gov (United States)

    Admal, Nikhil Chandra; Marian, Jaime; Po, Giacomo

    2017-02-01

    We derive the atomistic representations of the elastic tensors appearing in the linearized theory of first strain-gradient elasticity for an arbitrary multi-lattice. In addition to the classical (2nd-Piola) stress and elastic moduli tensors, these include the rank-three double-stress tensor, the rank-five tensor of mixed elastic moduli, and the rank-six tensor of strain-gradient elastic moduli. The atomistic representations are closed-form analytical expressions in terms of the first and second derivatives of the interatomic potential with respect to interatomic distances, and dyadic products of relative atomic positions. Moreover, all expressions are local, in the sense that they depend only on the atomic neighborhood of a lattice site. Our results emanate from the condition of energetic equivalence between continuum and atomistic representations of a crystal, when the kinematics of the latter is governed by the Cauchy-Born rule. Using the derived expressions, we prove that the odd-order tensors vanish if the lattice basis admits central-symmetry. The analytical expressions are implemented as a KIM compliant algorithm to compute the strain gradient elastic tensors for various materials. Numerical results are presented to compare representative interatomic potentials used in the literature for cubic crystals, including simple lattices and multi-lattices. We observe that central potentials exhibit generalized Cauchy relations for the rank-six tensor of strain-gradient elastic moduli. In addition, this tensor is found to be indefinite for many potentials. We discuss the relationship between indefiniteness and material stability. Finally, the atomistic representations are specialized to central potentials in simple lattices. These expressions are used with analytical potentials to study the sensitivity of the elastic tensors to the choice of the cutoff radius.

  6. Exchange Rates and Fundamentals.

    Science.gov (United States)

    Engel, Charles; West, Kenneth D.

    2005-01-01

    We show analytically that in a rational expectations present-value model, an asset price manifests near-random walk behavior if fundamentals are I (1) and the factor for discounting future fundamentals is near one. We argue that this result helps explain the well-known puzzle that fundamental variables such as relative money supplies, outputs,…

  7. A dynamic atomistic-continuum method for the simulation of crystalline materials

    CERN Document Server

    Huang Zhon Gy

    2002-01-01

    We present a coupled atomistic-continuum method for the modeling of defects and interface dynamics in crystalline materials. The method uses atomistic models such as molecular dynamics near defects and interfaces, and continuum models away from defects and interfaces. We propose a new class of matching conditions between the atomistic and the continuum regions. These conditions ensure the accurate passage of large-scale information between the atomistic and the continuum regions and at the same time minimize the reflection of phonons at the atomistic-continuum interface. They can be made adaptive by choosing appropriate weight functions. We present applications to dislocation dynamics, friction between two-dimensional crystal surfaces, and fracture dynamics. We compare results of the coupled method and of the detailed atomistic model.

  8. Development and assessment of atomistic models for predicting static friction coefficients

    Science.gov (United States)

    Jahangiri, Soran; Heverly-Coulson, Gavin S.; Mosey, Nicholas J.

    2016-08-01

    The friction coefficient relates friction forces to normal loads and plays a key role in fundamental and applied areas of science and technology. Despite its importance, the relationship between the friction coefficient and the properties of the materials forming a sliding contact is poorly understood. We illustrate how simple relationships regarding the changes in energy that occur during slip can be used to develop a quantitative model relating the friction coefficient to atomic-level features of the contact. The slip event is considered as an activated process and the load dependence of the slip energy barrier is approximated with a Taylor series expansion of the corresponding energies with respect to load. The resulting expression for the load-dependent slip energy barrier is incorporated in the Prandtl-Tomlinson (PT) model and a shear-based model to obtain expressions for friction coefficient. The results indicate that the shear-based model reproduces the static friction coefficients μs obtained from first-principles molecular dynamics simulations more accurately than the PT model. The ability of the model to provide atomistic explanations for differences in μs amongst different contacts is also illustrated. As a whole, the model is able to account for fundamental atomic-level features of μs, explain the differences in μs for different materials based on their properties, and might be also used in guiding the development of contacts with desired values of μs.

  9. Brand Aid

    DEFF Research Database (Denmark)

    Richey, Lisa Ann; Ponte, Stefano

    A critical account of the rise of celebrity-driven “compassionate consumption” Cofounded by the rock star Bono in 2006, Product RED exemplifies a new trend in celebrity-driven international aid and development, one explicitly linked to commerce, not philanthropy. Brand Aid offers a deeply informed...

  10. Foreign aid

    DEFF Research Database (Denmark)

    Tarp, Finn

    2008-01-01

    Foreign aid has evolved significantly since the Second World War in response to a dramatically changing global political and economic context. This article (a) reviews this process and associated trends in the volume and distribution of foreign aid; (b) reviews the goals, principles...

  11. Fundamentals of gas dynamics

    CERN Document Server

    Babu, V

    2014-01-01

    Fundamentals of Gas Dynamics, Second Edition isa comprehensively updated new edition and now includes a chapter on the gas dynamics of steam. It covers the fundamental concepts and governing equations of different flows, and includes end of chapter exercises based on the practical applications. A number of useful tables on the thermodynamic properties of steam are also included.Fundamentals of Gas Dynamics, Second Edition begins with an introduction to compressible and incompressible flows before covering the fundamentals of one dimensional flows and normal shock wav

  12. Atomistic Conversion Reaction Mechanism of WO 3 in Secondary Ion Batteries of Li, Na, and Ca

    Energy Technology Data Exchange (ETDEWEB)

    He, Yang [Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh PA 15261 USA; Gu, Meng [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA 99352 USA; Xiao, Haiyan [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 China; Luo, Langli [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA 99352 USA; Shao, Yuyan [Energy and Environmental Directorate, Pacific Northwest National Laboratory, Richland WA 99352 USA; Gao, Fei [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor MI 48109 USA; Du, Yingge [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA 99352 USA; Mao, Scott X. [Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh PA 15261 USA; Wang, Chongmin [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA 99352 USA

    2016-04-13

    Reversible insertion and extraction of ionic species into a host lattice governs the basic operating principle for both rechargeable battery (such as lithium batteries) and electrochromic devices (such as ANA Boeing 787-8 Dreamliner electrochromic window). Intercalation and/or conversion are two fundamental chemical processes for some materials in response to the ion insertion. The interplay between these two chemical processes has never been established. It is speculated that the conversion reaction is initiated by ion intercalation. However, experimental evidence of intercalation and subsequent conversion remains unexplored. Here, using in situ HRTEM and spectroscopy, we captured the atomistic conversion reaction processes during lithium, sodium and calcium ion insertion into tungsten trioxide (WO3) single crystal model electrodes. An intercalation step right prior to conversion is explicitly revealed at atomic scale for the first time for these three ion species. Combining nanoscale diffraction and ab initio molecular dynamics simulations, it is found that, beyond intercalation, the inserted ion-oxygen bonding formation destabilized the transition-metal framework which gradually shrunk, distorted and finally collapsed to a pseudo-amorphous structure. This study provides a full atomistic picture on the transition from intercalation to conversion, which is of essential for material applications in both secondary ion batteries and electrochromic devices.

  13. Microwave engineering concepts and fundamentals

    CERN Document Server

    Khan, Ahmad Shahid

    2014-01-01

    Detailing the active and passive aspects of microwaves, Microwave Engineering: Concepts and Fundamentals covers everything from wave propagation to reflection and refraction, guided waves, and transmission lines, providing a comprehensive understanding of the underlying principles at the core of microwave engineering. This encyclopedic text not only encompasses nearly all facets of microwave engineering, but also gives all topics—including microwave generation, measurement, and processing—equal emphasis. Packed with illustrations to aid in comprehension, the book: •Describes the mathematical theory of waveguides and ferrite devices, devoting an entire chapter to the Smith chart and its applications •Discusses different types of microwave components, antennas, tubes, transistors, diodes, and parametric devices •Examines various attributes of cavity resonators, semiconductor and RF/microwave devices, and microwave integrated circuits •Addresses scattering parameters and their properties, as well a...

  14. Fluid mechanics fundamentals and applications

    CERN Document Server

    Cengel, Yunus

    2013-01-01

    Cengel and Cimbala's Fluid Mechanics Fundamentals and Applications, communicates directly with tomorrow's engineers in a simple yet precise manner. The text covers the basic principles and equations of fluid mechanics in the context of numerous and diverse real-world engineering examples. The text helps students develop an intuitive understanding of fluid mechanics by emphasizing the physics, using figures, numerous photographs and visual aids to reinforce the physics. The highly visual approach enhances the learning of Fluid mechanics by students. This text distinguishes itself from others by the way the material is presented - in a progressive order from simple to more difficult, building each chapter upon foundations laid down in previous chapters. In this way, even the traditionally challenging aspects of fluid mechanics can be learned effectively. McGraw-Hill is also proud to offer ConnectPlus powered by Maple with the third edition of Cengel/Cimbabla, Fluid Mechanics. This innovative and powerful new sy...

  15. Atomistic simulation of the structural and elastic properties of magnesite

    Indian Academy of Sciences (India)

    ZI-JIANG LIU; XIAO-WEI SUN; TING SONG; YUAN GUO; CAI-RONG ZHANG; ZHENG-RONG ZHANG

    2016-09-01

    Atomistic simulation was carried out to study the structural and elastic properties of MgCO$_3$ magnesite within the pressure range of the Earth’s mantle based on a novel force field. The lattice parameters and elasticconstants as a function of pressure up to 150 GPa are calculated. The results are in good agreement with the available experimental data and previous theoretical results, showing no phase transition over the pressure range of interest. We also found that magnesite exhibits a strong anisotropy throughout the lower mantle and that the nature of the anisotropy changes significantly with depth.

  16. Predicting dislocation climb and creep from explicit atomistic details.

    Science.gov (United States)

    Kabir, Mukul; Lau, Timothy T; Rodney, David; Yip, Sidney; Van Vliet, Krystyn J

    2010-08-27

    Here we report kinetic Monte Carlo simulations of dislocation climb in heavily deformed, body-centered cubic iron comprising a supersaturation of vacancies. This approach explicitly incorporates the effect of nonlinear vacancy-dislocation interaction on vacancy migration barriers as determined from atomistic calculations, and enables observations of diffusivity and climb over time scales and temperatures relevant to power-law creep. By capturing the underlying microscopic physics, the calculated stress exponents for steady-state creep rates agree quantitatively with the experimentally measured range, and qualitatively with the stress dependence of creep activation energies.

  17. Atomistic Molecular Dynamics Simulations of Mitochondrial DNA Polymerase γ

    DEFF Research Database (Denmark)

    Euro, Liliya; Haapanen, Outi; Róg, Tomasz

    2017-01-01

    DNA polymerase γ (Pol γ) is a key component of the mitochondrial DNA replisome and an important cause of neurological diseases. Despite the availability of its crystal structures, the molecular mechanism of DNA replication, the switch between polymerase and exonuclease activities, the site...... of replisomal interactions, and functional effects of patient mutations that do not affect direct catalysis have remained elusive. Here we report the first atomistic classical molecular dynamics simulations of the human Pol γ replicative complex. Our simulation data show that DNA binding triggers remarkable...

  18. Interfacial Phenomena: Linking Atomistic and Molecular Level Processes

    Energy Technology Data Exchange (ETDEWEB)

    Jay A Brandes

    2009-09-23

    This was a grant to support travel for scientists to present data and interact with others in their field. Specifically, speakers presented their data in a session entitled “Interfacial Phenomena: Linking Atomistic and Macroscopic Properties: Theoretical and Experimental Studies of the Structure and Reactivity of Mineral Surfaces”. The session ran across three ½ day periods, March 30-31 2004. The session’s organizers were David J. Wesolowski andGordon E. Brown Jr. There were a total of 30 talks presented.

  19. Atomistic simulations of highly conductive molecular transport junctions under realistic conditions

    KAUST Repository

    French, William R.

    2013-01-01

    We report state-of-the-art atomistic simulations combined with high-fidelity conductance calculations to probe structure-conductance relationships in Au-benzenedithiolate (BDT)-Au junctions under elongation. Our results demonstrate that large increases in conductance are associated with the formation of monatomic chains (MACs) of Au atoms directly connected to BDT. An analysis of the electronic structure of the simulated junctions reveals that enhancement in the s-like states in Au MACs causes the increases in conductance. Other structures also result in increased conductance but are too short-lived to be detected in experiment, while MACs remain stable for long simulation times. Examinations of thermally evolved junctions with and without MACs show negligible overlap between conductance histograms, indicating that the increase in conductance is related to this unique structural change and not thermal fluctuation. These results, which provide an excellent explanation for a recently observed anomalous experimental result [Bruot et al., Nat. Nanotechnol., 2012, 7, 35-40], should aid in the development of mechanically responsive molecular electronic devices. © 2013 The Royal Society of Chemistry.

  20. Fundamentals of Physics

    Science.gov (United States)

    Halliday, David; Resnick, Robert; Walker, Jearl

    2003-01-01

    No other book on the market today can match the success of Halliday, Resnick and Walker's Fundamentals of Physics! In a breezy, easy-to-understand style the book offers a solid understanding of fundamental physics concepts, and helps readers apply this conceptual understanding to quantitative problem solving.

  1. Control of density fluctuations in atomistic-continuum simulations of dense liquids

    DEFF Research Database (Denmark)

    Kotsalis, E.M.; Walther, Jens Honore; Koumoutsakos, P.

    2007-01-01

    We present a control algorithm to eliminate spurious density fluctuations associated with the coupling of atomistic and continuum descriptions for dense liquids. A Schwartz domain decomposition algorithm is employed to couple molecular dynamics for the simulation of the atomistic system with a co...

  2. Going Backward : A Flexible Geometric Approach to Reverse Transformation from Coarse Grained to Atomistic Models

    NARCIS (Netherlands)

    Wassenaar, Tsjerk A.; Pluhackova, Kristyna; Böckmann, Rainer A.; Marrink, Siewert J.; Tieleman, D. Peter

    2014-01-01

    The conversion of coarse-grained to atomistic models is an important step in obtaining insight about atomistic scale processes from coarse-grained simulations. For this process, called backmapping or reverse transformation, several tools are available, but these commonly require libraries of molecul

  3. Coupling Length Scales for Multiscale Atomistics-Continuum Simulations: Atomistically Induced Stress Distributions in Si/Si{sub 3}N

    Energy Technology Data Exchange (ETDEWEB)

    Lidorikis, Elefterios; Bachlechner, Martina E.; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya; Voyiadjis, George Z.

    2001-08-20

    A hybrid molecular-dynamics (MD) and finite-element simulation approach is used to study stress distributions in silicon/silicon-nitride nanopixels. The hybrid approach provides atomistic description near the interface and continuum description deep into the substrate, increasing the accessible length scales and greatly reducing the computational cost. The results of the hybrid simulation are in good agreement with full multimillion-atom MD simulations: atomic structures at the lattice-mismatched interface between amorphous silicon nitride and silicon induce inhomogeneous stress patterns in the substrate that cannot be reproduced by a continuum approach alone.

  4. Hearing Aid

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A man realized that he needed to purchase ahearing aid, but he was unwilling to spend muchmoney. "How much do they run?"he asked theclerk. "That depends," said. the salesman. "Theyrun from 2 to 2000."

  5. Hearing Aids

    Science.gov (United States)

    ... slightly different from the ITC and is nearly hidden in the ear canal. Both canal hearing aids ... Privacy Policy & Terms of Use Visit the Nemours Web site. Note: All information on TeensHealth® is for ...

  6. Atomistic interpretation of solid solution hardening from spectral analysis.

    Science.gov (United States)

    Plendl, J N

    1971-05-01

    From analysis of a series of vibrational spectra of ir energy absorption and laser Raman, an attempt is made to interpret solid solution hardening from an atomistic point of view for the system CaF(2)/SrF(2). It is shown to be caused by the combined action of three atomic characteristics, i.e., their changes as a function of composition. They are deformation of the atomic coordination polyhedrons, overlap of the outer electron shells of the atom pairs, and the ratio of the ionic to covalent share of binding. A striking nonlinear behavior of the three characteristics, as a function of composition, gives maximum atomic bond strength to the 55/45 position of the system CaF(2)/SrF(2), in agreement with the measured data of the solid solution hardening. The curve for atomic bond strength, derived from the three characteristics, is almost identical to the curve for measured microhardness data. This result suggests that the atomistic interpretation, put forward in this paper, is correct.

  7. Void Coalescence Processes Quantified Through Atomistic and Multiscale Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Rudd, R E; Seppala, E T; Dupuy, L M; Belak, J

    2007-01-12

    Simulation of ductile fracture at the atomic scale reveals many aspects of the fracture process including specific mechanisms associated with void nucleation and growth as a precursor to fracture and the plastic deformation of the material surrounding the voids and cracks. Recently we have studied void coalescence in ductile metals using large-scale atomistic and continuum simulations. Here we review that work and present some related investigations. The atomistic simulations involve three-dimensional strain-controlled multi-million atom molecular dynamics simulations of copper. The correlated growth of two voids during the coalescence process leading to fracture is investigated, both in terms of its onset and the ensuing dynamical interactions. Void interactions are quantified through the rate of reduction of the distance between the voids, through the correlated directional growth of the voids, and through correlated shape evolution of the voids. The critical inter-void ligament distance marking the onset of coalescence is shown to be approximately one void radius based on the quantification measurements used, independent of the initial separation distance between the voids and the strain-rate of the expansion of the system. No pronounced shear flow is found in the coalescence process. We also discuss a technique for optimizing the calculation of fine-scale information on the fly for use in a coarse-scale simulation, and discuss the specific case of a fine-scale model that calculates void growth explicitly feeding into a coarse-scale mechanics model to study damage localization.

  8. Void Coalescence Processes Quantified through Atomistic and Multiscale Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Rudd, R E; Seppala, E T; Dupuy, L M; Belak, J

    2005-12-31

    Simulation of ductile fracture at the atomic scale reveals many aspects of the fracture process including specific mechanisms associated with void nucleation and growth as a precursor to fracture and the plastic deformation of the material surrounding the voids and cracks. Recently we have studied void coalescence in ductile metals using large-scale atomistic and continuum simulations. Here we review that work and present some related investigations. The atomistic simulations involve three-dimensional strain-controlled multi-million atom molecular dynamics simulations of copper. The correlated growth of two voids during the coalescence process leading to fracture is investigated, both in terms of its onset and the ensuing dynamical interactions. Void interactions are quantified through the rate of reduction of the distance between the voids, through the correlated directional growth of the voids, and through correlated shape evolution of the voids. The critical inter-void ligament distance marking the onset of coalescence is shown to be approximately one void radius based on the quantification measurements used, independent of the initial separation distance between the voids and the strain-rate of the expansion of the system. No pronounced shear flow is found in the coalescence process.

  9. Adaptive resolution simulation of an atomistic protein in MARTINI water

    Science.gov (United States)

    Zavadlav, Julija; Melo, Manuel Nuno; Marrink, Siewert J.; Praprotnik, Matej

    2014-02-01

    We present an adaptive resolution simulation of protein G in multiscale water. We couple atomistic water around the protein with mesoscopic water, where four water molecules are represented with one coarse-grained bead, farther away. We circumvent the difficulties that arise from coupling to the coarse-grained model via a 4-to-1 molecule coarse-grain mapping by using bundled water models, i.e., we restrict the relative movement of water molecules that are mapped to the same coarse-grained bead employing harmonic springs. The water molecules change their resolution from four molecules to one coarse-grained particle and vice versa adaptively on-the-fly. Having performed 15 ns long molecular dynamics simulations, we observe within our error bars no differences between structural (e.g., root-mean-squared deviation and fluctuations of backbone atoms, radius of gyration, the stability of native contacts and secondary structure, and the solvent accessible surface area) and dynamical properties of the protein in the adaptive resolution approach compared to the fully atomistically solvated model. Our multiscale model is compatible with the widely used MARTINI force field and will therefore significantly enhance the scope of biomolecular simulations.

  10. 3d visualization of atomistic simulations on every desktop

    Science.gov (United States)

    Peled, Dan; Silverman, Amihai; Adler, Joan

    2013-08-01

    Once upon a time, after making simulations, one had to go to a visualization center with fancy SGI machines to run a GL visualization and make a movie. More recently, OpenGL and its mesa clone have let us create 3D on simple desktops (or laptops), whether or not a Z-buffer card is present. Today, 3D a la Avatar is a commodity technique, presented in cinemas and sold for home TV. However, only a few special research centers have systems large enough for entire classes to view 3D, or special immersive facilities like visualization CAVEs or walls, and not everyone finds 3D immersion easy to view. For maximum physics with minimum effort a 3D system must come to each researcher and student. So how do we create 3D visualization cheaply on every desktop for atomistic simulations? After several months of attempts to select commodity equipment for a whole room system, we selected an approach that goes back a long time, even predating GL. The old concept of anaglyphic stereo relies on two images, slightly displaced, and viewed through colored glasses, or two squares of cellophane from a regular screen/projector or poster. We have added this capability to our AViz atomistic visualization code in its new, 6.1 version, which is RedHat, CentOS and Ubuntu compatible. Examples using data from our own research and that of other groups will be given.

  11. Fundamentals of electronics

    CERN Document Server

    Schubert, Thomas F

    2015-01-01

    This book, Electronic Devices and Circuit Application, is the first of four books of a larger work, Fundamentals of Electronics. It is comprised of four chapters describing the basic operation of each of the four fundamental building blocks of modern electronics: operational amplifiers, semiconductor diodes, bipolar junction transistors, and field effect transistors. Attention is focused on the reader obtaining a clear understanding of each of the devices when it is operated in equilibrium. Ideas fundamental to the study of electronic circuits are also developed in the book at a basic level to

  12. Multiscale atomistic simulation of metal-oxygen surface interactions: Methodological development, theoretical investigation, and correlation with experiment

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Judith C. [Univ. of Pittsburgh, Pittsburgh, PA (United States)

    2015-01-09

    The purpose of this grant is to develop the multi-scale theoretical methods to describe the nanoscale oxidation of metal thin films, as the PI (Yang) extensive previous experience in the experimental elucidation of the initial stages of Cu oxidation by primarily in situ transmission electron microscopy methods. Through the use and development of computational tools at varying length (and time) scales, from atomistic quantum mechanical calculation, force field mesoscale simulations, to large scale Kinetic Monte Carlo (KMC) modeling, the fundamental underpinings of the initial stages of Cu oxidation have been elucidated. The development of computational modeling tools allows for accelerated materials discovery. The theoretical tools developed from this program impact a wide range of technologies that depend on surface reactions, including corrosion, catalysis, and nanomaterials fabrication.

  13. Lattice Thermal Conductivity from Atomistic Simulations: ZrB2 and HfB2

    Science.gov (United States)

    Lawson, John W.; Daw, Murray S.; Bauschlicher, Charles W.

    2012-01-01

    Ultra high temperature ceramics (UHTC) including ZrB2 and HfB2 have a number of properties that make them attractive for applications in extreme environments. One such property is their high thermal conductivity. Computational modeling of these materials will facilitate understanding of fundamental mechanisms, elucidate structure-property relationships, and ultimately accelerate the materials design cycle. Progress in computational modeling of UHTCs however has been limited in part due to the absence of suitable interatomic potentials. Recently, we developed Tersoff style parameterizations of such potentials for both ZrB2 and HfB2 appropriate for atomistic simulations. As an application, Green-Kubo molecular dynamics simulations were performed to evaluate the lattice thermal conductivity for single crystals of ZrB2 and HfB2. The atomic mass difference in these binary compounds leads to oscillations in the time correlation function of the heat current, in contrast to the more typical monotonic decay seen in monoatomic materials such as Silicon, for example. Results at room temperature and at elevated temperatures will be reported.

  14. Fundamentals of electrochemical science

    CERN Document Server

    Oldham, Keith

    1993-01-01

    Key Features* Deals comprehensively with the basic science of electrochemistry* Treats electrochemistry as a discipline in its own right and not as a branch of physical or analytical chemistry* Provides a thorough and quantitative description of electrochemical fundamentals

  15. Fundamentals of crystallography

    CERN Document Server

    2011-01-01

    Crystallography is a basic tool for scientists in many diverse disciplines. This text offers a clear description of fundamentals and of modern applications. It supports curricula in crystallography at undergraduate level.

  16. Information security fundamentals

    CERN Document Server

    Peltier, Thomas R

    2013-01-01

    Developing an information security program that adheres to the principle of security as a business enabler must be the first step in an enterprise's effort to build an effective security program. Following in the footsteps of its bestselling predecessor, Information Security Fundamentals, Second Edition provides information security professionals with a clear understanding of the fundamentals of security required to address the range of issues they will experience in the field.The book examines the elements of computer security, employee roles and r

  17. Fundamentals of structural dynamics

    CERN Document Server

    Craig, Roy R

    2006-01-01

    From theory and fundamentals to the latest advances in computational and experimental modal analysis, this is the definitive, updated reference on structural dynamics.This edition updates Professor Craig's classic introduction to structural dynamics, which has been an invaluable resource for practicing engineers and a textbook for undergraduate and graduate courses in vibrations and/or structural dynamics. Along with comprehensive coverage of structural dynamics fundamentals, finite-element-based computational methods, and dynamic testing methods, this Second Edition includes new and e

  18. Masses of Fundamental Particles

    CERN Document Server

    Terazawa, Hidezumi

    2011-01-01

    Not only the masses of fundamental particles including the weak bosons, Higgs scalar, quarks, and leptons, but also the mixing angles of quarks and those of neutrinos are all explained and/or predicted in the unified composite model of quarks and leptons successfully. In addition, both of the two anomalies recently found by the CDF Collaboration are suggested to be taken as evidences for the substructure of the fundamental particles.

  19. Amp: A modular approach to machine learning in atomistic simulations

    Science.gov (United States)

    Khorshidi, Alireza; Peterson, Andrew A.

    2016-10-01

    Electronic structure calculations, such as those employing Kohn-Sham density functional theory or ab initio wavefunction theories, have allowed for atomistic-level understandings of a wide variety of phenomena and properties of matter at small scales. However, the computational cost of electronic structure methods drastically increases with length and time scales, which makes these methods difficult for long time-scale molecular dynamics simulations or large-sized systems. Machine-learning techniques can provide accurate potentials that can match the quality of electronic structure calculations, provided sufficient training data. These potentials can then be used to rapidly simulate large and long time-scale phenomena at similar quality to the parent electronic structure approach. Machine-learning potentials usually take a bias-free mathematical form and can be readily developed for a wide variety of systems. Electronic structure calculations have favorable properties-namely that they are noiseless and targeted training data can be produced on-demand-that make them particularly well-suited for machine learning. This paper discusses our modular approach to atomistic machine learning through the development of the open-source Atomistic Machine-learning Package (Amp), which allows for representations of both the total and atom-centered potential energy surface, in both periodic and non-periodic systems. Potentials developed through the atom-centered approach are simultaneously applicable for systems with various sizes. Interpolation can be enhanced by introducing custom descriptors of the local environment. We demonstrate this in the current work for Gaussian-type, bispectrum, and Zernike-type descriptors. Amp has an intuitive and modular structure with an interface through the python scripting language yet has parallelizable fortran components for demanding tasks; it is designed to integrate closely with the widely used Atomic Simulation Environment (ASE), which

  20. The relative entropy is fundamental to adaptive resolution simulations

    Science.gov (United States)

    Kreis, Karsten; Potestio, Raffaello

    2016-07-01

    Adaptive resolution techniques are powerful methods for the efficient simulation of soft matter systems in which they simultaneously employ atomistic and coarse-grained (CG) force fields. In such simulations, two regions with different resolutions are coupled with each other via a hybrid transition region, and particles change their description on the fly when crossing this boundary. Here we show that the relative entropy, which provides a fundamental basis for many approaches in systematic coarse-graining, is also an effective instrument for the understanding of adaptive resolution simulation methodologies. We demonstrate that the use of coarse-grained potentials which minimize the relative entropy with respect to the atomistic system can help achieve a smoother transition between the different regions within the adaptive setup. Furthermore, we derive a quantitative relation between the width of the hybrid region and the seamlessness of the coupling. Our results do not only shed light on the what and how of adaptive resolution techniques but will also help setting up such simulations in an optimal manner.

  1. Types of Hearing Aids

    Science.gov (United States)

    ... Devices Consumer Products Hearing Aids Types of Hearing Aids Share Tweet Linkedin Pin it More sharing options ... some features for hearing aids? What are hearing aids? Hearing aids are sound-amplifying devices designed to ...

  2. Material fields in atomistics as pull-backs of spatial distributions

    Science.gov (United States)

    Chandra Admal, Nikhil; Tadmor, Ellad B.

    2016-04-01

    The various fields defined in continuum mechanics have both a material and a spatial description that are related through the deformation mapping. In contrast, continuum fields defined for atomistic systems using the Irving-Kirkwood or Murdoch-Hardy procedures correspond to a spatial description. It is uncommon to define atomistic fields in the reference configuration due to the lack of a unique definition for the deformation mapping in atomistic systems. In this paper, we construct referential atomistic distributions as pull-backs of the spatial distributions obtained in the Murdoch-Hardy procedure with respect to a postulated deformation mapping that tracks particles. We then show that some of these referential distributions are independent of the choice of the deformation mapping and only depend on the reference and current configuration of particles. Therefore, the fields obtained from these distributions can be calculated without explicitly constructing a deformation map, and by construction they satisfy the balance equations. In particular, we obtain definitions for the first and second atomistic Piola-Kirchhoff stress tensors. We demonstrate the validity of these definitions through a numerical example involving finite deformation of a slab containing a notch under tension. An interesting feature of the atomistic first Piola-Kirchhoff stress tensor is the absence of a kinetic part, which in the atomistic Cauchy stress tensor accounts for thermal fluctuations. We show that this effect is implicitly included in the atomistic first Piola-Kirchhoff stress tensor through the motion of the particles. An open source program to compute the atomistic Cauchy and first Piola-Kirchhoff stress fields called MDStressLab is available online at

  3. Variation of Fundamental Constants

    Science.gov (United States)

    Flambaum, V. V.

    2006-11-01

    Theories unifying gravity with other interactions suggest temporal and spatial variation of the fundamental ``constants'' in expanding Universe. The spatial variation can explain a fine tuning of the fundamental constants which allows humans (and any life) to appear. We appeared in the area of the Universe where the values of the fundamental constants are consistent with our existence. We present a review of recent works devoted to the variation of the fine structure constant α, strong interaction and fundamental masses. There are some hints for the variation in quasar absorption spectra. Big Bang nucleosynthesis, and Oklo natural nuclear reactor data. A very promising method to search for the variation of the fundamental constants consists in comparison of different atomic clocks. Huge enhancement of the variation effects happens in transition between accidentally degenerate atomic and molecular energy levels. A new idea is to build a ``nuclear'' clock based on the ultraviolet transition between very low excited state and ground state in Thorium nucleus. This may allow to improve sensitivity to the variation up to 10 orders of magnitude! Huge enhancement of the variation effects is also possible in cold atomic and molecular collisions near Feshbach resonance.

  4. Atomistic simulation of static magnetic properties of bit patterned media

    Science.gov (United States)

    Arbeláez-Echeverri, O. D.; Agudelo-Giraldo, J. D.; Restrepo-Parra, E.

    2016-09-01

    In this work we present a new design of Co based bit pattern media with out-of-plane uni-axial anisotropy induced by interface effects. Our model features the inclusion of magnetic impurities in the non-magnetic matrix. After the material model was refined during three iterations using Monte Carlo simulations, further simulations were performed using an atomistic integrator of Landau-Lifshitz-Gilbert equation with Langevin dynamics to study the behavior of the system paying special attention to the super-paramagnetic limit. Our model system exhibits three magnetic phase transitions, one due to the magnetically doped matrix material and the weak magnetic interaction between the nano-structures in the system. The different magnetic phases of the system as well as the features of its phase diagram are explained.

  5. Atomistic Hydrodynamics and the Dynamical Hydrophobic Effect in Porous Graphene.

    Science.gov (United States)

    Strong, Steven E; Eaves, Joel D

    2016-05-19

    Mirroring their role in electrical and optical physics, two-dimensional crystals are emerging as novel platforms for fluid separations and water desalination, which are hydrodynamic processes that occur in nanoscale environments. For numerical simulation to play a predictive and descriptive role, one must have theoretically sound methods that span orders of magnitude in physical scales, from the atomistic motions of particles inside the channels to the large-scale hydrodynamic gradients that drive transport. Here, we use constraint dynamics to derive a nonequilibrium molecular dynamics method for simulating steady-state mass flow of a fluid moving through the nanoscopic spaces of a porous solid. After validating our method on a model system, we use it to study the hydrophobic effect of water moving through pores of electrically doped single-layer graphene. The trend in permeability that we calculate does not follow the hydrophobicity of the membrane but is instead governed by a crossover between two competing molecular transport mechanisms.

  6. Shock Hugoniot behavior of single crystal titanium using atomistic simulations

    Science.gov (United States)

    Mackenchery, Karoon; Dongare, Avinash

    2017-01-01

    Atomistic shock simulations are performed for single crystal titanium using four different interatomic potentials at impact velocities ranging from 0.5 km/s to 2.0 km/s. These potentials comprise of three parameterizations in the formulation of the embedded atom method and one formulation of the modified embedded atom method. The capability of the potentials to model the shock deformation and failure behavior is investigated by computing the shock hugoniot response of titanium and comparing to existing experimental data. In addition, the capability to reproduce the shock induced alpha (α) to omega (ω) phase transformation seen in Ti is investigated. The shock wave structure is discussed and the velocities for the elastic, plastic and the α-ω phase transformation waves are calculated for all the interatomic potentials considered.

  7. Effective Transparency: A Test of Atomistic Laser-Cluster Models

    CERN Document Server

    Pandit, Rishi; Teague, Thomas; Hartwick, Zachary; Bigaouette, Nicolas; Ramunno, Lora; Ackad, Edward

    2016-01-01

    The effective transparency of rare-gas clusters, post-interaction with an extreme ultraviolet (XUV) pump pulse, is studied by using an atomistic hybrid quantum-classical molecular dynamics model. We find there is an intensity range in which an XUV probe pulse has no lasting effect on the average charge state of a cluster after being saturated by an XUV pump pulse: the cluster is effectively transparent to the probe pulse. The range of this phenomena increases with the size of the cluster and thus provides an excellent candidate for an experimental test of the effective transparency effect. We present predictions for the clusters at the peak of the laser pulse as well as the experimental time-of-flight signal expected along with trends which can be compared with. Significant deviations from these predictions would provide evidence for enhanced photoionization mechanism(s).

  8. Effects of Atomistic Domain Size on Hybrid Lattice Boltzmann-Molecular Dynamics Simulations of Dense Fluids

    Science.gov (United States)

    Dupuis, A.; Koumoutsakos, P.

    We present a convergence study for a hybrid Lattice Boltzmann-Molecular Dynamics model for the simulation of dense liquids. Time and length scales are decoupled by using an iterative Schwarz domain decomposition algorithm. The velocity field from the atomistic domain is introduced as forcing terms to the Lattice Boltzmann model of the continuum while the mean field of the continuum imposes mean field conditions for the atomistic domain. In the present paper we investigate the effect of varying the size of the atomistic subdomain in simulations of two dimensional flows of liquid argon past carbon nanotubes and assess the efficiency of the method.

  9. Fundamentals of turbomachines

    CERN Document Server

    Dick, Erik

    2015-01-01

    This book explores the working principles of all kinds of turbomachines. The same theoretical framework is used to analyse the different machine types. Fundamentals are first presented and theoretical concepts are then elaborated for particular machine types, starting with the simplest ones.For each machine type, the author strikes a balance between building basic understanding and exploring knowledge of practical aspects. Readers are invited through challenging exercises to consider how the theory applies to particular cases and how it can be generalised.   The book is primarily meant as a course book. It teaches fundamentals and explores applications. It will appeal to senior undergraduate and graduate students in mechanical engineering and to professional engineers seeking to understand the operation of turbomachines. Readers will gain a fundamental understanding of turbomachines. They will also be able to make a reasoned choice of turbomachine for a particular application and to understand its operation...

  10. Pragmatic electrical engineering fundamentals

    CERN Document Server

    Eccles, William

    2011-01-01

    Pragmatic Electrical Engineering: Fundamentals introduces the fundamentals of the energy-delivery part of electrical systems. It begins with a study of basic electrical circuits and then focuses on electrical power. Three-phase power systems, transformers, induction motors, and magnetics are the major topics.All of the material in the text is illustrated with completely-worked examples to guide the student to a better understanding of the topics. This short lecture book will be of use at any level of engineering, not just electrical. Its goal is to provide the practicing engineer with a practi

  11. Fundamentals of continuum mechanics

    CERN Document Server

    Rudnicki, John W

    2014-01-01

    A concise introductory course text on continuum mechanics Fundamentals of Continuum Mechanics focuses on the fundamentals of the subject and provides the background for formulation of numerical methods for large deformations and a wide range of material behaviours. It aims to provide the foundations for further study, not just of these subjects, but also the formulations for much more complex material behaviour and their implementation computationally.  This book is divided into 5 parts, covering mathematical preliminaries, stress, motion and deformation, balance of mass, momentum and energ

  12. Fundamentals of magnetism

    CERN Document Server

    Reis, Mario

    2013-01-01

    The Fundamentals of Magnetism is a truly unique reference text, that explores the study of magnetism and magnetic behavior with a depth that no other book can provide. It covers the most detailed descriptions of the fundamentals of magnetism providing an emphasis on statistical mechanics which is absolutely critical for understanding magnetic behavior. The books covers the classical areas of basic magnetism, including Landau Theory and magnetic interactions, but features a more concise and easy-to-read style. Perfect for upper-level graduate students and industry researchers, The Fu

  13. Homeschooling and religious fundamentalism

    Directory of Open Access Journals (Sweden)

    Robert KUNZMAN

    2010-10-01

    Full Text Available This article considers the relationship between homeschooling and religious fundamentalism by focusing on their intersection in the philosophies and practices of conservative Christian homeschoolers in the United States. Homeschooling provides an ideal educational setting to support several core fundamentalist principles: resistance to contemporary culture; suspicion of institutional authority and professional expertise; parental control and centrality of the family; and interweaving of faith and academics. It is important to recognize, however, that fundamentalism exists on a continuum; conservative religious homeschoolers resist liberal democratic values to varying degrees, and efforts to foster dialogue and accommodation with religious homeschoolers can ultimately helpstrengthen the broader civic fabric.

  14. Fundamentals of nonlinear optics

    CERN Document Server

    Powers, Peter E

    2011-01-01

    Peter Powers's rigorous but simple description of a difficult field keeps the reader's attention throughout. … All chapters contain a list of references and large numbers of practice examples to be worked through. … By carefully working through the proposed problems, students will develop a sound understanding of the fundamental principles and applications. … the book serves perfectly for an introductory-level course for second- and third-order nonlinear optical phenomena. The author's writing style is refreshing and original. I expect that Fundamentals of Nonlinear Optics will fast become pop

  15. Infosec management fundamentals

    CERN Document Server

    Dalziel, Henry

    2015-01-01

    Infosec Management Fundamentals is a concise overview of the Information Security management concepts and techniques, providing a foundational template for both experienced professionals and those new to the industry. This brief volume will also appeal to business executives and managers outside of infosec who want to understand the fundamental concepts of Information Security and how it impacts their business decisions and daily activities. Teaches ISO/IEC 27000 best practices on information security management Discusses risks and controls within the context of an overall information securi

  16. Antennas fundamentals, design, measurement

    CERN Document Server

    Long, Maurice

    2009-01-01

    This comprehensive revision (3rd Edition) is a senior undergraduate or first-year graduate level textbook on antenna fundamentals, design, performance analysis, and measurements. In addition to its use as a formal course textbook, the book's pragmatic style and emphasis on the fundamentals make it especially useful to engineering professionals who need to grasp the essence of the subject quickly but without being mired in unnecessary detail. This new edition was prepared for a first year graduate course at Southern Polytechnic State University in Georgia. It provides broad coverage of antenna

  17. Brand Aid

    DEFF Research Database (Denmark)

    Richey, Lisa Ann; Ponte, Stefano

    2011-01-01

    activists, scholars and venture capitalists, discusses the pros and cons of changing the world by ‘voting with your dollars’. Lisa Ann Richey and Stefano Ponte (Professor at Roskilde University and Senior Researcher at DIIS respectively), authors of Brand Aid: Shopping Well to Save the World, highlight how...

  18. Fundamentals of soil science

    Science.gov (United States)

    This study guide provides comments and references for professional soil scientists who are studying for the soil science fundamentals exam needed as the first step for certification. The performance objectives were determined by the Soil Science Society of America's Council of Soil Science Examiners...

  19. Homeschooling and Religious Fundamentalism

    Science.gov (United States)

    Kunzman, Robert

    2010-01-01

    This article considers the relationship between homeschooling and religious fundamentalism by focusing on their intersection in the philosophies and practices of conservative Christian homeschoolers in the United States. Homeschooling provides an ideal educational setting to support several core fundamentalist principles: resistance to…

  20. Fundamentals and Optimal Institutions

    DEFF Research Database (Denmark)

    Gonzalez-Eiras, Martin; Harmon, Nikolaj Arpe; Rossi, Martín

    2016-01-01

    of regulatory institutions such as revenue sharing, salary caps or luxury taxes. We show, theoretically and empirically, that these large differences in adopted institutions can be rationalized as optimal responses to differences in the fundamental characteristics of the sports being played. This provides...

  1. Fundamental Metallurgy of Solidification

    DEFF Research Database (Denmark)

    Tiedje, Niels

    2004-01-01

    The text takes the reader through some fundamental aspects of solidification, with focus on understanding the basic physics that govern solidification in casting and welding. It is described how the first solid is formed and which factors affect nucleation. It is described how crystals grow from ...

  2. Fundamentals of convolutional coding

    CERN Document Server

    Johannesson, Rolf

    2015-01-01

    Fundamentals of Convolutional Coding, Second Edition, regarded as a bible of convolutional coding brings you a clear and comprehensive discussion of the basic principles of this field * Two new chapters on low-density parity-check (LDPC) convolutional codes and iterative coding * Viterbi, BCJR, BEAST, list, and sequential decoding of convolutional codes * Distance properties of convolutional codes * Includes a downloadable solutions manual

  3. Fundamental Physics Microgravity Sensitivity

    Science.gov (United States)

    Israelsson, Ulf

    1998-01-01

    An introduction followed by a brief discussion about the sensitivity to microgravity environment disturbances for some recent and planned experiments in microgravity fundamental physics will be presented. In particular, correlation between gravity disturbances and the quality of science data sets measured by the Confined Helium Experiment (CHEX) during ground testing and during the November 1997 USMP-4 flight will be described.

  4. Fundamental partial compositeness

    DEFF Research Database (Denmark)

    Sannino, Francesco; Strumia, Alessandro; Tesi, Andrea

    2016-01-01

    We construct renormalizable Standard Model extensions, valid up to the Planck scale, that give a composite Higgs from a new fundamental strong force acting on fermions and scalars. Yukawa interactions of these particles with Standard Model fermions realize the partial compositeness scenario. Unde...

  5. Fundamentals of Business Economics

    OpenAIRE

    2013-01-01

    Powerpoint presentations of the 9 theoretical units of the subject: Fundamentals of Business Economics. Business Administration Degree. Faculty of Economics. University of Alicante En el marco de ayudas a preparación de materiales docentes en lengua inglesa, por parte del Servei de Política Llingüística de la Universidad de Alicante

  6. Fundamentals of astrodynamics

    NARCIS (Netherlands)

    Wakker, K.F.

    2015-01-01

    This book deals with the motion of the center of mass of a spacecraft; this discipline is generally called astrodynamics. The book focuses on an analytical treatment of the motion of spacecraft and provides insight into the fundamentals of spacecraft orbit dynamics. A large number of topics are trea

  7. Fundamentals of plasma physics

    CERN Document Server

    Bittencourt, J A

    1986-01-01

    A general introduction designed to present a comprehensive, logical and unified treatment of the fundamentals of plasma physics based on statistical kinetic theory. Its clarity and completeness make it suitable for self-learning and self-paced courses. Problems are included.

  8. A Comparative Study of China's Foreign Aid

    Institute of Scientific and Technical Information of China (English)

    Huang Ying

    2007-01-01

    Chinese development assistance is totally different in nature in comparison with the aid offered by the United States and Japan. The U.S. sees its aid as a form of "mercy" to less-developed countries and gives it with numerous conditions attached. Japan seems to mainly use it to pursue commercial interests. By contrast, Chinese aid is, in essence, cooperation and mutual support between developing countries. This fundamental difference helps to explain why Beijing's aid is so different from that of the Western donors.

  9. Control of density fluctuations in atomistic-continuum simulations of dense liquids

    Science.gov (United States)

    Kotsalis, E. M.; Walther, J. H.; Koumoutsakos, P.

    2007-07-01

    We present a control algorithm to eliminate spurious density fluctuations associated with the coupling of atomistic and continuum descriptions for dense liquids. A Schwartz domain decomposition algorithm is employed to couple molecular dynamics for the simulation of the atomistic system with a continuum solver for the simulation of the Navier-Stokes equations. The lack of periodic boundary conditions in the molecular dynamics simulations hinders the proper accounting for the virial pressure leading to spurious density fluctuations at the continuum-atomistic interface. An ad hoc boundary force is usually employed to remedy this situation. We propose the calculation of this boundary force using a control algorithm that explicitly cancels the density fluctuations. The results demonstrate that the present approach outperforms state-of-the-art algorithms. The conceptual and algorithmic simplicity of the method makes it suitable for any type of coupling between atomistic and continuum descriptions of dense fluids.

  10. Hybrid simulations: combining atomistic and coarse-grained force fields using virtual sites.

    Science.gov (United States)

    Rzepiela, Andrzej J; Louhivuori, Martti; Peter, Christine; Marrink, Siewert J

    2011-06-14

    Hybrid simulations, in which part of the system is represented at atomic resolution and the remaining part at a reduced, coarse-grained, level offer a powerful way to combine the accuracy associated with the atomistic force fields to the sampling speed obtained with coarse-grained (CG) potentials. In this work we introduce a straightforward scheme to perform hybrid simulations, making use of virtual sites to couple the two levels of resolution. With the help of these virtual sites interactions between molecules at different levels of resolution, i.e. between CG and atomistic molecules, are treated the same way as the pure CG-CG interactions. To test our method, we combine the Gromos atomistic force field with a number of coarse-grained potentials, obtained through several approaches that are designed to obtain CG potentials based on an existing atomistic model, namely iterative Boltzmann inversion, force matching, and a potential of mean force subtraction procedure (SB). We also explore the use of the MARTINI force field for the CG potential. A simple system, consisting of atomistic butane molecules dissolved in CG butane, is used to study the performance of our hybrid scheme. Based on the potentials of mean force for atomistic butane in CG solvent, and the properties of 1:1 mixtures of atomistic and CG butane which should exhibit ideal mixing behavior, we conclude that the MARTINI and SB potentials are particularly suited to be combined with the atomistic force field. The MARTINI potential is subsequently used to perform hybrid simulations of atomistic dialanine peptides in both CG butane and water. Compared to a fully atomistic description of the system, the hybrid description gives similar results provided that the dielectric screening of water is accounted for. Within the field of biomolecules, our method appears ideally suited to study e.g. protein-ligand binding, where the active site and ligand are modeled in atomistic detail and the rest of the protein

  11. Fundamental Enabling Issues in Nanotechnology: Stress at the Atomic Scale

    Energy Technology Data Exchange (ETDEWEB)

    Floro, Jerrold Anthony [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Univ. of Virginia, Charlottesville, VA (United States). Dept. of Materials Science and Engineering; Foiles, Stephen Martin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hearne, Sean Joseph [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hoyt, Jeffrey John [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); McMaster Univ., Hamilton, ON (Canada); Seel, Steven Craig [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Emcore Corporation, Albuquerque, NM (United States); Webb, Edmund Blackburn [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Morales, Alfredo Martin [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Zimmerman, Jonathan A. [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2007-10-01

    To effectively integrate nanotechnology into functional devices, fundamental aspects of material behavior at the nanometer scale must be understood. Stresses generated during thin film growth strongly influence component lifetime and performance; stress has also been proposed as a mechanism for stabilizing supported nanoscale structures. Yet the intrinsic connections between the evolving morphology of supported nanostructures and stress generation are still a matter of debate. This report presents results from a combined experiment and modeling approach to study stress evolution during thin film growth. Fully atomistic simulations are presented predicting stress generation mechanisms and magnitudes during all growth stages, from island nucleation to coalescence and film thickening. Simulations are validated by electrodeposition growth experiments, which establish the dependence of microstructure and growth stresses on process conditions and deposition geometry. Sandia is one of the few facilities with the resources to combine experiments and modeling/theory in this close a fashion. Experiments predicted an ongoing coalescence process that generates signficant tensile stress. Data from deposition experiments also support the existence of a kinetically limited compressive stress generation mechanism. Atomistic simulations explored island coalescence and deposition onto surfaces intersected by grain boundary structures to permit investigation of stress evolution during later growth stages, e.g., continual island coalescence and adatom incorporation into grain boundaries. The predictive capabilities of simulation permit direct determination of fundamental processes active in stress generation at the nanometer scale while connecting those processes, via new theory, to continuum models for much larger island and film structures. Our combined experiment and simulation results reveal the necessary materials science to tailor stress, and therefore performance, in

  12. Atomistic study of crack propagation and dislocation emission in Cu-Ni multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Clinedinst, J.; Farkas, D. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering

    1997-09-01

    The authors present atomistic simulations of the crack tip configuration in multilayered Cu-Ni materials. The simulations were carried out using molecular statics and EAM potentials. The atomistic structure of the interface was studied first for a totally coherent structure. Cracks were simulated near a Griffith condition in different possible configurations of the crack plane and front with respect to the axis of the layers. Results show that interface effects predominantly control the mechanical behavior of the system studied.

  13. Tactile Aids

    Directory of Open Access Journals (Sweden)

    Mohtaramossadat Homayuni

    1996-04-01

    Full Text Available Tactile aids, which translate sound waves into vibrations that can be felt by the skin, have been used for decades by people with severe/profound hearing loss to enhance speech/language development and improve speechreading.The development of tactile aids dates from the efforts of Goults and his co-workers in the 1920s; Although The power supply was too voluminous and it was difficult to carry specially by children, it was too huge and heavy to be carried outside the laboratories and its application was restricted to the experimental usage. Nowadays great advances have been performed in producing this instrument and its numerous models is available in markets around the world.

  14. Negotiating Aid

    DEFF Research Database (Denmark)

    Whitfield, Lindsay; Fraser, Alastair

    2011-01-01

    This article presents a new analytical approach to the study of aid negotiations. Building on existing approaches but trying to overcome their limitations, it argues that factors outside of individual negotiations (or the `game' in game-theoretic approaches) significantly affect the preferences...... of actors, the negotiating strategies they fashion, and the success of those strategies. This approach was employed to examine and compare the experiences of eight countries: Botswana, Ethiopia, Ghana, Mali, Mozambique, Rwanda, Tanzania and Zambia. The article presents findings from these country studies...... which investigated the strategies these states have adopted in talks with aid donors, the sources of leverage they have been able to bring to bear in negotiations, and the differing degrees of control that they have been able to exercise over the policies agreed in negotiations and those implemented...

  15. Three-dimensional Hybrid Continuum-Atomistic Simulations for Multiscale Hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Wijesinghe, S; Hornung, R; Garcia, A; Hadjiconstantinou, N

    2004-04-15

    We present an adaptive mesh and algorithmic refinement (AMAR) scheme for modeling multi-scale hydrodynamics. The AMAR approach extends standard conservative adaptive mesh refinement (AMR) algorithms by providing a robust flux-based method for coupling an atomistic fluid representation to a continuum model. The atomistic model is applied locally in regions where the continuum description is invalid or inaccurate, such as near strong flow gradients and at fluid interfaces, or when the continuum grid is refined to the molecular scale. The need for such ''hybrid'' methods arises from the fact that hydrodynamics modeled by continuum representations are often under-resolved or inaccurate while solutions generated using molecular resolution globally are not feasible. In the implementation described herein, Direct Simulation Monte Carlo (DSMC) provides an atomistic description of the flow and the compressible two-fluid Euler equations serve as our continuum-scale model. The AMR methodology provides local grid refinement while the algorithm refinement feature allows the transition to DSMC where needed. The continuum and atomistic representations are coupled by matching fluxes at the continuum-atomistic interfaces and by proper averaging and interpolation of data between scales. Our AMAR application code is implemented in C++ and is built upon the SAMRAI (Structured Adaptive Mesh Refinement Application Infrastructure) framework developed at Lawrence Livermore National Laboratory. SAMRAI provides the parallel adaptive gridding algorithm and enables the coupling between the continuum and atomistic methods.

  16. Nano sculpt: A methodology for generating complex realistic configurations for atomistic simulations.

    Science.gov (United States)

    Prakash, A; Hummel, M; Schmauder, S; Bitzek, E

    2016-01-01

    Atomistic simulations have now become commonplace in the study of the deformation and failure of materials. Increase in computing power in recent years has made large-scale simulations with billions, or even trillions, of atoms a possibility. Most simulations to-date, however, are still performed with quasi-2D geometries or rather simplistic 3D setups. Although controlled studies on such well-defined structures are often required to obtain quantitative information from atomistic simulations, for qualitative studies focusing on e.g. the identification of mechanisms, researchers would greatly benefit from a methodology that helps realize more realistic configurations. The ideal scenario would be a one-on-one reconstruction of experimentally observed structures. To this end, we propose a new method and software tool called nano sculpt with the following features:•The method allows for easy sample generation for atomistic simulations from any arbitrarily shaped 3D enclosed volume.•The tool can be used to build atomistic samples from artificial geometries, including CAD geometries and structures obtained from simulation methods other than atomistic simulations.•The tool enables the generation of experimentally informed atomistic samples, by e.g. digitization of micrographs or usage of tomography data.

  17. Fundamentals of differential beamforming

    CERN Document Server

    Benesty, Jacob; Pan, Chao

    2016-01-01

    This book provides a systematic study of the fundamental theory and methods of beamforming with differential microphone arrays (DMAs), or differential beamforming in short. It begins with a brief overview of differential beamforming and some popularly used DMA beampatterns such as the dipole, cardioid, hypercardioid, and supercardioid, before providing essential background knowledge on orthogonal functions and orthogonal polynomials, which form the basis of differential beamforming. From a physical perspective, a DMA of a given order is defined as an array that measures the differential acoustic pressure field of that order; such an array has a beampattern in the form of a polynomial whose degree is equal to the DMA order. Therefore, the fundamental and core problem of differential beamforming boils down to the design of beampatterns with orthogonal polynomials. But certain constraints also have to be considered so that the resulting beamformer does not seriously amplify the sensors’ self noise and the mism...

  18. Fundamentals of nuclear physics

    CERN Document Server

    Takigawa, Noboru

    2017-01-01

    This book introduces the current understanding of the fundamentals of nuclear physics by referring to key experimental data and by providing a theoretical understanding of principal nuclear properties. It primarily covers the structure of nuclei at low excitation in detail. It also examines nuclear forces and decay properties. In addition to fundamentals, the book treats several new research areas such as non-relativistic as well as relativistic Hartree–Fock calculations, the synthesis of super-heavy elements, the quantum chromodynamics phase diagram, and nucleosynthesis in stars, to convey to readers the flavor of current research frontiers in nuclear physics. The authors explain semi-classical arguments and derivation of its formulae. In these ways an intuitive understanding of complex nuclear phenomena is provided. The book is aimed at graduate school students as well as junior and senior undergraduate students and postdoctoral fellows. It is also useful for researchers to update their knowledge of diver...

  19. Fundamental stellar parameters

    CERN Document Server

    Wittkowski, M

    2004-01-01

    I present a discussion of fundamental stellar parameters and their observational determination in the context of interferometric measurements with current and future optical/infrared interferometric facilities. Stellar parameters and the importance of their determination for stellar physics are discussed. One of the primary uses of interferometry in the field of stellar physics is the measurement of the intensity profile across the stellar disk, both as a function of position angle and of wavelength. High-precision fundamental stellar parameters are also derived by characterizations of binary and multiple system using interferometric observations. This topic is discussed in detail elsewhere in these proceedings. Comparison of observed spectrally dispersed center-to-limb intensity variations with models of stellar atmospheres and stellar evolution may result in an improved understanding of key phenomena in stellar astrophysics such as the precise evolutionary effects on the main sequence, the evolution of meta...

  20. Variation of fundamental constants

    CERN Document Server

    Flambaum, V V

    2006-01-01

    We present a review of recent works devoted to the variation of the fine structure constant alpha, strong interaction and fundamental masses. There are some hints for the variation in quasar absorption spectra, Big Bang nucleosynthesis, and Oklo natural nuclear reactor data. A very promising method to search for the variation of the fundamental constants consists in comparison of different atomic clocks. Huge enhancement of the variation effects happens in transition between accidentally degenerate atomic and molecular energy levels. A new idea is to build a ``nuclear'' clock based on the ultraviolet transition between very low excited state and ground state in Thorium nucleus. This may allow to improve sensitivity to the variation up to 10 orders of magnitude! Huge enhancement of the variation effects is also possible in cold atomic and molecular collisions near Feschbach resonance.

  1. What is Fundamental?

    CERN Multimedia

    2004-01-01

    Discussing what is fundamental in a variety of fields, biologist Richard Dawkins, physicist Gerardus 't Hooft, and mathematician Alain Connes spoke to a packed Main Auditorium at CERN 15 October. Dawkins, Professor of the Public Understanding of Science at Oxford University, explained simply the logic behind Darwinian natural selection, and how it would seem to apply anywhere in the universe that had the right conditions. 't Hooft, winner of the 1999 Physics Nobel Prize, outlined some of the main problems in physics today, and said he thinks physics is so fundamental that even alien scientists from another planet would likely come up with the same basic principles, such as relativity and quantum mechanics. Connes, winner of the 1982 Fields Medal (often called the Nobel Prize of Mathematics), explained how physics is different from mathematics, which he described as a "factory for concepts," unfettered by connection to the physical world. On 16 October, anthropologist Sharon Traweek shared anecdotes from her ...

  2. Fundamentals of neurobiology.

    Science.gov (United States)

    Greg Hall, D

    2011-01-01

    Session 1 of the 2010 STP/IFSTP Joint Symposium on Toxicologic Neuropathology, titled "Fundamentals of Neurobiology," was organized to provide a foundation for subsequent sessions by presenting essential elements of neuroanatomy and nervous system function. A brief introduction to the session titled "Introduction to Correlative Neurobiology" was provided by Dr. Greg Hall (Eli Lilly and Company, Indianapolis, IN). Correlative neurobiology refers to considerations of the relationships between the highly organized and compartmentalized structure of nervous tissues and the functioning within this system.

  3. Fundamentals of linear algebra

    CERN Document Server

    Dash, Rajani Ballav

    2008-01-01

    FUNDAMENTALS OF LINEAR ALGEBRA is a comprehensive Text Book, which can be used by students and teachers of All Indian Universities. The Text has easy, understandable form and covers all topics of UGC Curriculum. There are lots of worked out examples which helps the students in solving the problems without anybody's help. The Problem sets have been designed keeping in view of the questions asked in different examinations.

  4. Fundamentals of Stochastic Networks

    CERN Document Server

    Ibe, Oliver C

    2011-01-01

    An interdisciplinary approach to understanding queueing and graphical networks In today's era of interdisciplinary studies and research activities, network models are becoming increasingly important in various areas where they have not regularly been used. Combining techniques from stochastic processes and graph theory to analyze the behavior of networks, Fundamentals of Stochastic Networks provides an interdisciplinary approach by including practical applications of these stochastic networks in various fields of study, from engineering and operations management to communications and the physi

  5. Fundamentals of Biomechanics

    OpenAIRE

    Duane Knudson

    2007-01-01

    DESCRIPTION This book provides a broad and in-depth theoretical and practical description of the fundamental concepts in understanding biomechanics in the qualitative analysis of human movement. PURPOSE The aim is to bring together up-to-date biomechanical knowledge with expert application knowledge. Extensive referencing for students is also provided. FEATURES This textbook is divided into 12 chapters within four parts, including a lab activities section at the end. The division is as follow...

  6. Fundamentals of Monte Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Wollaber, Allan Benton [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-06-16

    This is a powerpoint presentation which serves as lecture material for the Parallel Computing summer school. It goes over the fundamentals of the Monte Carlo calculation method. The material is presented according to the following outline: Introduction (background, a simple example: estimating π), Why does this even work? (The Law of Large Numbers, The Central Limit Theorem), How to sample (inverse transform sampling, rejection), and An example from particle transport.

  7. Biomedical engineering fundamentals

    CERN Document Server

    Bronzino, Joseph D

    2014-01-01

    Known as the bible of biomedical engineering, The Biomedical Engineering Handbook, Fourth Edition, sets the standard against which all other references of this nature are measured. As such, it has served as a major resource for both skilled professionals and novices to biomedical engineering.Biomedical Engineering Fundamentals, the first volume of the handbook, presents material from respected scientists with diverse backgrounds in physiological systems, biomechanics, biomaterials, bioelectric phenomena, and neuroengineering. More than three dozen specific topics are examined, including cardia

  8. High voltage engineering fundamentals

    CERN Document Server

    Kuffel, E; Hammond, P

    1984-01-01

    Provides a comprehensive treatment of high voltage engineering fundamentals at the introductory and intermediate levels. It covers: techniques used for generation and measurement of high direct, alternating and surge voltages for general application in industrial testing and selected special examples found in basic research; analytical and numerical calculation of electrostatic fields in simple practical insulation system; basic ionisation and decay processes in gases and breakdown mechanisms of gaseous, liquid and solid dielectrics; partial discharges and modern discharge detectors; and over

  9. Fundamentals of Business

    OpenAIRE

    Skripak, Stephen J.

    2016-01-01

    Fundamentals of Business (2016) is an openly licensed (CC BY NC SA 3.0) textbook designed for use in Virginia Tech’s Pamplin College of Business introductory level business course, MGT1104 Foundations of Business. This work is a project of University Libraries and the Pamplin College of Business, Virginia Tech.Lead Author: Stephen J. SkripakContributors: Richard Parsons, Anastasia Cortes, Anita WalzLayout: Anastasia Cortes Selected graphics: Brian Craig http://bcraigdesign.comCover design:...

  10. Fundamentals of queueing theory

    CERN Document Server

    Gross, Donald; Thompson, James M; Harris, Carl M

    2013-01-01

    Praise for the Third Edition ""This is one of the best books available. Its excellent organizational structure allows quick reference to specific models and its clear presentation . . . solidifies the understanding of the concepts being presented.""-IIE Transactions on Operations Engineering Thoroughly revised and expanded to reflect the latest developments in the field, Fundamentals of Queueing Theory, Fourth Edition continues to present the basic statistical principles that are necessary to analyze the probabilistic nature of queues. Rather than pre

  11. Neutrons and Fundamental Symmetries

    Energy Technology Data Exchange (ETDEWEB)

    Plaster, Bradley [Univ. of Kentucky, Lexington, KY (United States). Dept. of Physics and Astronomy

    2016-01-11

    The research supported by this project addressed fundamental open physics questions via experiments with subatomic particles. In particular, neutrons constitute an especially ideal “laboratory” for fundamental physics tests, as their sensitivities to the four known forces of nature permit a broad range of tests of the so-called “Standard Model”, our current best physics model for the interactions of subatomic particles. Although the Standard Model has been a triumphant success for physics, it does not provide satisfactory answers to some of the most fundamental open questions in physics, such as: are there additional forces of nature beyond the gravitational, electromagnetic, weak nuclear, and strong nuclear forces?, or why does our universe consist of more matter than anti-matter? This project also contributed significantly to the training of the next generation of scientists, of considerable value to the public. Young scientists, ranging from undergraduate students to graduate students to post-doctoral researchers, made significant contributions to the work carried out under this project.

  12. Value of Fundamental Science

    Science.gov (United States)

    Burov, Alexey

    Fundamental science is a hard, long-term human adventure that has required high devotion and social support, especially significant in our epoch of Mega-science. The measure of this devotion and this support expresses the real value of the fundamental science in public opinion. Why does fundamental science have value? What determines its strength and what endangers it? The dominant answer is that the value of science arises out of curiosity and is supported by the technological progress. Is this really a good, astute answer? When trying to attract public support, we talk about the ``mystery of the universe''. Why do these words sound so attractive? What is implied by and what is incompatible with them? More than two centuries ago, Immanuel Kant asserted an inseparable entanglement between ethics and metaphysics. Thus, we may ask: which metaphysics supports the value of scientific cognition, and which does not? Should we continue to neglect the dependence of value of pure science on metaphysics? If not, how can this issue be addressed in the public outreach? Is the public alienated by one or another message coming from the face of science? What does it mean to be politically correct in this sort of discussion?

  13. Atomistic modeling of electronic structure and transport in disordered nanostructures

    Science.gov (United States)

    Kharche, Neerav

    As the Si-CMOS technology approaches the end of the International Technology Roadmap for Semiconductors (ITRS), the semiconductor industry faces a formidable challenge to continue the transistor scaling according to Moore's law. To continue the scaling of classical devices, alternative channel materials such as SiGe, carbon nanotubes, nanowires, and III-V based materials are being investigated along with novel 3D device geometries. Researchers are also investigating radically new quantum computing devices, which are expected to perform calculations faster than the existing classical Si-CMOS based structures. Atomic scale disorders such as interface roughness, alloy randomness, non-uniform strain, and dopant fluctuations are routinely present in the experimental realization of such devices. These disorders now play an increasingly important role in determining the electronic structure and transport properties as device sizes enter the nanometer regime. This work employs the atomistic tight-binding technique, which is ideally suited for modeling systems with local disorders on an atomic scale. High-precision multi-million atom electronic structure calculations of (111) Si surface quantum wells and (100) SiGe/Si/SiGe heterostructure quantum wells are performed to investigate the modulation of valley splitting induced by atomic scale disorders. The calculations presented here resolve the existing discrepancies between theoretically predicted and experimentally measured valley splitting, which is an important design parameter in quantum computing devices. Supercell calculations and the zone-unfolding method are used to compute the bandstructures of inhomogeneous nanowires made of AlGaAs and SiGe and their connection with the transmission coefficients computed using non-equilibrium Green's function method is established. A unified picture of alloy nanowires emerges, in which the nanodevice (transmission) and nanomaterials (bandstructure) viewpoints complement each other

  14. Mathematics for natural scientists fundamentals and basics

    CERN Document Server

    Kantorovich, Lev

    2016-01-01

    This book, the first in a two part series, covers a course of mathematics tailored specifically for physics, engineering and chemistry students at the undergraduate level. It is unique in that it begins with logical concepts of mathematics first encountered at A-level and covers them in thorough detail, filling in the gaps in students' knowledge and reasoning. Then the book aids the leap between A-level and university-level mathematics, with complete proofs provided throughout and all complex mathematical concepts and techniques presented in a clear and transparent manner. Numerous examples and problems (with answers) are given for each section and, where appropriate, mathematical concepts are illustrated in a physics context. This text gives an invaluable foundation to students and a comprehensive aid to lecturers. Mathematics for Natural Scientists: Fundamentals and Basics is the first of two volumes. Advanced topics and their applications in physics are covered in the second volume.

  15. Optimization Algorithms in Optimal Predictions of Atomistic Properties by Kriging.

    Science.gov (United States)

    Di Pasquale, Nicodemo; Davie, Stuart J; Popelier, Paul L A

    2016-04-12

    The machine learning method kriging is an attractive tool to construct next-generation force fields. Kriging can accurately predict atomistic properties, which involves optimization of the so-called concentrated log-likelihood function (i.e., fitness function). The difficulty of this optimization problem quickly escalates in response to an increase in either the number of dimensions of the system considered or the size of the training set. In this article, we demonstrate and compare the use of two search algorithms, namely, particle swarm optimization (PSO) and differential evolution (DE), to rapidly obtain the maximum of this fitness function. The ability of these two algorithms to find a stationary point is assessed by using the first derivative of the fitness function. Finally, the converged position obtained by PSO and DE is refined through the limited-memory Broyden-Fletcher-Goldfarb-Shanno bounded (L-BFGS-B) algorithm, which belongs to the class of quasi-Newton algorithms. We show that both PSO and DE are able to come close to the stationary point, even in high-dimensional problems. They do so in a reasonable amount of time, compared to that with the Newton and quasi-Newton algorithms, regardless of the starting position in the search space of kriging hyperparameters. The refinement through L-BFGS-B is able to give the position of the maximum with whichever precision is desired.

  16. Dislocation climb models from atomistic scheme to dislocation dynamics

    Science.gov (United States)

    Niu, Xiaohua; Luo, Tao; Lu, Jianfeng; Xiang, Yang

    2017-02-01

    We develop a mesoscopic dislocation dynamics model for vacancy-assisted dislocation climb by upscalings from a stochastic model on the atomistic scale. Our models incorporate microscopic mechanisms of (i) bulk diffusion of vacancies, (ii) vacancy exchange dynamics between bulk and dislocation core, (iii) vacancy pipe diffusion along the dislocation core, and (iv) vacancy attachment-detachment kinetics at jogs leading to the motion of jogs. Our mesoscopic model consists of the vacancy bulk diffusion equation and a dislocation climb velocity formula. The effects of these microscopic mechanisms are incorporated by a Robin boundary condition near the dislocations for the bulk diffusion equation and a new contribution in the dislocation climb velocity due to vacancy pipe diffusion driven by the stress variation along the dislocation. Our climb formulation is able to quantitatively describe the translation of prismatic loops at low temperatures when the bulk diffusion is negligible. Using this new formulation, we derive analytical formulas for the climb velocity of a straight edge dislocation and a prismatic circular loop. Our dislocation climb formulation can be implemented in dislocation dynamics simulations to incorporate all the above four microscopic mechanisms of dislocation climb.

  17. Transistor roadmap projection using predictive full-band atomistic modeling

    Energy Technology Data Exchange (ETDEWEB)

    Salmani-Jelodar, M., E-mail: m.salmani@gmail.com; Klimeck, G. [Network for Computational Nanotechnology and School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Kim, S. [Intel Corporation, 2501 Northwest 229th Avenue, Hillsboro, Oregon 97124 (United States); Ng, K. [Semiconductor Research Corporation (SRC), 1101 Slater Rd, Durham, North Carolina 27703 (United States)

    2014-08-25

    In this letter, a full band atomistic quantum transport tool is used to predict the performance of double gate metal-oxide-semiconductor field-effect transistors (MOSFETs) over the next 15 years for International Technology Roadmap for Semiconductors (ITRS). As MOSFET channel lengths scale below 20 nm, the number of atoms in the device cross-sections becomes finite. At this scale, quantum mechanical effects play an important role in determining the device characteristics. These quantum effects can be captured with the quantum transport tool. Critical results show the ON-current degradation as a result of geometry scaling, which is in contrast to previous ITRS compact model calculations. Geometric scaling has significant effects on the ON-current by increasing source-to-drain (S/D) tunneling and altering the electronic band structure. By shortening the device gate length from 20 nm to 5.1 nm, the ratio of S/D tunneling current to the overall subthreshold OFF-current increases from 18% to 98%. Despite this ON-current degradation by scaling, the intrinsic device speed is projected to increase at a rate of at least 8% per year as a result of the reduction of the quantum capacitance.

  18. Scoring multipole electrostatics in condensed-phase atomistic simulations.

    Science.gov (United States)

    Bereau, Tristan; Kramer, Christian; Monnard, Fabien W; Nogueira, Elisa S; Ward, Thomas R; Meuwly, Markus

    2013-05-09

    Permanent multipoles (MTPs) embody a natural extension to common point-charge (PC) representations in atomistic simulations. In this work, we propose an alternative to the computationally expensive MTP molecular dynamics simulations by running a simple PC simulation and later reevaluate-"score''-all energies using the more detailed MTP force field. The method, which relies on the assumption that the PC and MTP force fields generate closely related phase spaces, is accomplished by enforcing identical sets of monopoles between the two force fields-effectively highlighting the higher MTP terms as a correction to the PC approximation. We first detail our consistent parametrization of the electrostatics and van der Waals interactions for the two force fields. We then validate the method by comparing the accuracy of protein-ligand binding free energies from both PC and MTP-scored representations with experimentally determined binding constants obtained by us. Specifically, we study the binding of several arylsulfonamide ligands to human carbonic anhydrase II. We find that both representations yield an accuracy of 1 kcal/mol with respect to experiment. Finally, we apply the method to rank the energetic contributions of individual atomic MTP coefficients for molecules solvated in water. All in all, MTP scoring is a computationally appealing method that can provide insight into the multipolar electrostatic interactions of condensed-phase systems.

  19. Atomistic Simulations of Uranium Incorporation into Iron (Hydr)Oxides

    Energy Technology Data Exchange (ETDEWEB)

    Kerisit, Sebastien N.; Felmy, Andrew R.; Ilton, Eugene S.

    2011-04-29

    Atomistic simulations were carried out to characterize the coordination environments of U incorporated in three Fe-(hydr)oxide minerals: goethite, magnetite, and hematite. The simulations provided information on U-O and U-Fe distances, coordination numbers, and lattice distortion for U incorporated in different sites (e.g., unoccupied versus occupied sites, octahedral versus tetrahedral) as a function of the oxidation state of U and charge compensation mechanisms (i.e., deprotonation, vacancy formation, or reduction of Fe(III) to Fe(II)). For goethite, deprotonation of first shell hydroxyls enables substitution of U for Fe(III) with a minimal amount of lattice distortion, whereas substitution in unoccupied octahedral sites induced appreciable distortion to 7-fold coordination regardless of U oxidation states and charge compensation mechanisms. Importantly, U-Fe distances of ~3.6 Å were associated with structural incorporation of U and cannot be considered diagnostic of simple adsorption to goethite surfaces. For magnetite, the octahedral site accommodates U(V) or U(VI) with little lattice distortion. U substituted for Fe(III) in hematite maintained octahedral coordination in most cases. In general, comparison of the simulations with available experimental data provides further evidence for the structural incorporation of U in iron (hydr)oxide minerals.

  20. Atomistic modeling at experimental strain rates and timescales

    Science.gov (United States)

    Yan, Xin; Cao, Penghui; Tao, Weiwei; Sharma, Pradeep; Park, Harold S.

    2016-12-01

    Modeling physical phenomena with atomistic fidelity and at laboratory timescales is one of the holy grails of computational materials science. Conventional molecular dynamics (MD) simulations enable the elucidation of an astonishing array of phenomena inherent in the mechanical and chemical behavior of materials. However, conventional MD, with our current computational modalities, is incapable of resolving timescales longer than microseconds (at best). In this short review article, we briefly review a recently proposed approach—the so-called autonomous basin climbing (ABC) method—that in certain instances can provide valuable information on slow timescale processes. We provide a general summary of the principles underlying the ABC approach, with emphasis on recent methodological developments enabling the study of mechanically-driven processes at slow (experimental) strain rates and timescales. Specifically, we show that by combining a strong physical understanding of the underlying phenomena, kinetic Monte Carlo, transition state theory and minimum energy pathway methods, the ABC method has been found to be useful in a variety of mechanically-driven problems ranging from the prediction of creep-behavior in metals, constitutive laws for grain boundary sliding, void nucleation rates, diffusion in amorphous materials to protein unfolding. Aside from reviewing the basic ideas underlying this approach, we emphasize some of the key challenges encountered in our own personal research work and suggest future research avenues for exploration.

  1. Atomistic modeling of H absorption in Pd nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ruda, M., E-mail: ruda@cab.cnea.gov.a [Centro Atomico Bariloche, 8400 Bariloche (Argentina); Centro Regional Universitario Bariloche, U.N. Comahue (Argentina); Crespo, E.A., E-mail: crespo@uncoma.edu.a [Depto. de Fisica, Fac. de Ingenieria, Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquen (Argentina); Debiaggi, S. Ramos de, E-mail: ramos@uncoma.edu.a [Depto. de Fisica, Fac. de Ingenieria, Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquen (Argentina); CONICET (Argentina)

    2010-04-16

    Size affects the properties of absorption of H in Palladium nanoparticles. Because of their higher proportion of surface atoms compared to the bulk, the pressure-composition (P-C) isotherms of the nanoparticles are modified. We performed atomistic simulations for different-sized Pd nanoparticles and for the bulk at different H concentrations using the Monte Carlo technique in the TP{mu}N ensemble to calculate the P-C isotherms. The Pd-H interatomic potentials are of the Embedded Atom (EAM) type and have been recently developed by Zhou et al. . From the related van't Hoff equation we obtained |{Delta}H{sup o}| = (28 {+-} 7) kJ/0.5 mol of H{sub 2} and |{Delta}S{sup o}| = (71 {+-} 19) J/0.5 mol of H{sub 2}.K for the PdH formation in the bulk. For Pd nanoparticles previous simulations results based on a different set of EAM potentials showed that H was absorbed primarily in the surface before diffusing into the inside of small Pd clusters . Considering the better performance of Zhou's potentials for the bulk, in this work we analyzed the evolution of the equilibrium microstructure of Pd nanoparticles as a function of their size and H concentration. Our simulations predict enhanced hydrogen solubilities and vanishing plateaux when compared to the bulk and that H is absorbed in the subsurface of the nanoparticles.

  2. Atomistic modeling of phonon transport in turbostratic graphitic structures

    Science.gov (United States)

    Mao, Rui; Chen, Yifeng; Kim, Ki Wook

    2016-05-01

    Thermal transport in turbostratic graphitic systems is investigated by using an atomistic analytical model based on the 4th-nearest-neighbor force constant approximation and a registry-dependent interlayer potential. The developed model is shown to produce an excellent agreement with the experimental data and ab initio results in the calculation of bulk properties. Subsequent analysis of phonon transport in combination with the Green's function method illustrates the significant dependence of key characteristics on the misorientation angle, clearly indicating the importance of this degree of freedom in multi-stacked structures. Selecting three angles with the smallest commensurate unit cells, the thermal resistance is evaluated at the twisted interface between two AB stacked graphite. The resulting values in the range of 35 × 10-10 K m2/W to 116 × 10-10 K m2/W are as large as those between two dissimilar material systems such as a metal and graphene. The strong rotational effect on the cross-plane thermal transport may offer an effective means of phonon engineering for applications such as thermoelectric materials.

  3. Atomistic simulation of hydrogen dynamics near dislocations in vanadium hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, Hiroshi, E-mail: h.ogawa@aist.go.jp

    2015-10-05

    Highlights: • Hydrogen–dislocation interaction was simulated by molecular dynamics method. • Different distribution of H atoms were observed at edge and screw dislocation. • Planner distribution of hydrogen may be caused by partialized edge dislocation. • Hydrogen diffusivity was reduced in both edge and screw dislocation models. • Pipe diffusion was observed for edge dislocation but not for screw dislocation. - Abstract: Kinetics of interstitial hydrogen atoms near dislocation cores were analyzed by atomistic simulation. Classical molecular dynamics method was applied to model structures of edge and screw dislocations in α-phase vanadium hydride. Simulation showed that hydrogen atoms aggregate near dislocation cores. The spatial distribution of hydrogen has a planner shape at edge dislocation due to dislocation partialization, and a cylindrical shape at screw dislocation. Simulated self-diffusion coefficients of hydrogen atoms in dislocation models were a half- to one-order lower than that of dislocation-free model. Arrhenius plot of self-diffusivity showed slightly different activation energies for edge and screw dislocations. Directional dependency of hydrogen diffusion near dislocation showed high and low diffusivity along edge and screw dislocation lines, respectively, hence so called ‘pipe diffusion’ possibly occur at edge dislocation but does not at screw dislocation.

  4. Atomistic Molecular Dynamics Simulations of Shock Compressed Quartz

    CERN Document Server

    Farrow, Matthew R

    2011-01-01

    Atomistic non-equilibrium molecular dynamics (NEMD) simulations of shock wave compression of quartz have been performed using the so-called BKS semi-empirical potential of van Beest, Kramer and van Santen to construct the Hugoniot of quartz. Our scheme mimics the real world experimental set up by using a flyer-plate impactor to initiate the shock wave and is the first shock wave simulation that uses a geom- etry optimised system of a polar slab in a 3-dimensional system employing periodic boundary conditions. Our scheme also includes the relaxation of the surface dipole in the polar quartz slab which is an essential pre-requisite to a stable simulation. The original BKS potential is unsuited to shock wave calculations and so we propose a simple modification. With this modification, we find that our calculated Hugoniot is in good agreement with experimental shock wave data up to 25 GPa, but significantly diverges beyond this point. We conclude that our modified BKS potential is suitable for quartz under repres...

  5. Teaching AIDS.

    Science.gov (United States)

    Short, R V

    1989-06-01

    This article reviews a peer group Acquired Immunodeficiency Syndrome (AIDS) educational program at a university in Australia. Studies in the US have shown that most adolescents, although sexually active, do not believe they are likely to become infected with the Human Immunodeficiency Virus, and therefore do not attempt to modify their sexual behavior. A 1st step in educating students is to introduce them to condoms and impress upon them the fact that condoms should be used at the beginning of all sexual relationships, whether homosexual or heterosexual. In this program 3rd year medical students were targeted, as they are effective communicators and disseminators of information to the rest of the student body. After class members blow up condoms, giving them a chance to handle various brands and observe the varying degrees of strength, statistical evidence about the contraceptive failure rate of condoms (0.6-14.7 per 100 women-years) is discussed. Spermicides, such as nonoxynol-9 used in conjunction with condoms, are also discussed, as are condoms for women, packaging and marketing of condoms, including those made from latex and from the caecum of sheep, the latter condoms being of questionable effectiveness in preventing transmission of the virus. The care of terminal AIDS cases and current global and national statistics on AIDS are presented. The program also includes cash prizes for the best student essays on condom use, the distribution of condoms, condom key rings and T-shirts, and a student-run safe sex stand during orientation week. All of these activities are intended to involve students and attract the interest of the undergraduate community. Questionnaires administered to students at the end of the course revealed that the lectures were received favorably. Questionnaires administered to new medical and English students attending orientation week revealed that 72% of students thought the stand was a good idea and 81% and 83%, respectively found it

  6. FUNDAMENTALS OF BIOMECHANICS

    Directory of Open Access Journals (Sweden)

    Duane Knudson

    2007-09-01

    Full Text Available DESCRIPTION This book provides a broad and in-depth theoretical and practical description of the fundamental concepts in understanding biomechanics in the qualitative analysis of human movement. PURPOSE The aim is to bring together up-to-date biomechanical knowledge with expert application knowledge. Extensive referencing for students is also provided. FEATURES This textbook is divided into 12 chapters within four parts, including a lab activities section at the end. The division is as follows: Part 1 Introduction: 1.Introduction to biomechanics of human movement; 2.Fundamentals of biomechanics and qualitative analysis; Part 2 Biological/Structural Bases: 3.Anatomical description and its limitations; 4.Mechanics of the musculoskeletal system; Part 3 Mechanical Bases: 5.Linear and angular kinematics; 6.Linear kinetics; 7.Angular kinetics; 8.Fluid mechanics; Part 4 Application of Biomechanics in Qualitative Analysis :9.Applying biomechanics in physical education; 10.Applying biomechanics in coaching; 11.Applying biomechanics in strength and conditioning; 12.Applying biomechanics in sports medicine and rehabilitation. AUDIENCE This is an important reading for both student and educators in the medicine, sport and exercise-related fields. For the researcher and lecturer it would be a helpful guide to plan and prepare more detailed experimental designs or lecture and/or laboratory classes in exercise and sport biomechanics. ASSESSMENT The text provides a constructive fundamental resource for biomechanics, exercise and sport-related students, teachers and researchers as well as anyone interested in understanding motion. It is also very useful since being clearly written and presenting several ways of examples of the application of biomechanics to help teach and apply biomechanical variables and concepts, including sport-related ones

  7. Brand Aid

    DEFF Research Database (Denmark)

    Richey, Lisa Ann; Ponte, Stefano

    2011-01-01

    activists, scholars and venture capitalists, discusses the pros and cons of changing the world by ‘voting with your dollars’. Lisa Ann Richey and Stefano Ponte (Professor at Roskilde University and Senior Researcher at DIIS respectively), authors of Brand Aid: Shopping Well to Save the World, highlight how......Can Citizen Consumers Make a Difference? DIIS researcher contributes to a Boston Review - New Democracy Forum In the current issue of Boston Review (November/December 2011), contributors to a ‘New Democracy Forum’ debate whether Citizen Consumers can make a difference in stimulating responsible...

  8. Fundamental of biomedical engineering

    CERN Document Server

    Sawhney, GS

    2007-01-01

    About the Book: A well set out textbook explains the fundamentals of biomedical engineering in the areas of biomechanics, biofluid flow, biomaterials, bioinstrumentation and use of computing in biomedical engineering. All these subjects form a basic part of an engineer''s education. The text is admirably suited to meet the needs of the students of mechanical engineering, opting for the elective of Biomedical Engineering. Coverage of bioinstrumentation, biomaterials and computing for biomedical engineers can meet the needs of the students of Electronic & Communication, Electronic & Instrumenta

  9. Fundamentals of Project Management

    CERN Document Server

    Heagney, Joseph

    2011-01-01

    With sales of more than 160,000 copies, Fundamentals of Project Management has helped generations of project managers navigate the ins and outs of every aspect of this complex discipline. Using a simple step-by-step approach, the book is the perfect introduction to project management tools, techniques, and concepts. Readers will learn how to: ò Develop a mission statement, vision, goals, and objectives ò Plan the project ò Create the work breakdown structure ò Produce a workable schedule ò Understand earned value analysis ò Manage a project team ò Control and evaluate progress at every stage.

  10. Mathematical analysis fundamentals

    CERN Document Server

    Bashirov, Agamirza

    2014-01-01

    The author's goal is a rigorous presentation of the fundamentals of analysis, starting from elementary level and moving to the advanced coursework. The curriculum of all mathematics (pure or applied) and physics programs include a compulsory course in mathematical analysis. This book will serve as can serve a main textbook of such (one semester) courses. The book can also serve as additional reading for such courses as real analysis, functional analysis, harmonic analysis etc. For non-math major students requiring math beyond calculus, this is a more friendly approach than many math-centric o

  11. Fundamental concepts of mathematics

    CERN Document Server

    Goodstein, R L

    Fundamental Concepts of Mathematics, 2nd Edition provides an account of some basic concepts in modern mathematics. The book is primarily intended for mathematics teachers and lay people who wants to improve their skills in mathematics. Among the concepts and problems presented in the book include the determination of which integral polynomials have integral solutions; sentence logic and informal set theory; and why four colors is enough to color a map. Unlike in the first edition, the second edition provides detailed solutions to exercises contained in the text. Mathematics teachers and people

  12. Fundamentals of microwave photonics

    CERN Document Server

    Urick, V J; McKinney , Jason D

    2015-01-01

    A comprehensive resource to designing andconstructing analog photonic links capable of high RFperformanceFundamentals of Microwave Photonics provides acomprehensive description of analog optical links from basicprinciples to applications.  The book is organized into fourparts. The first begins with a historical perspective of microwavephotonics, listing the advantages of fiber optic links anddelineating analog vs. digital links. The second section coversbasic principles associated with microwave photonics in both the RFand optical domains.  The third focuses on analog modulationformats-starti

  13. Fundamentals of attosecond optics

    CERN Document Server

    Chang, Zenghu

    2011-01-01

    Attosecond optical pulse generation, along with the related process of high-order harmonic generation, is redefining ultrafast physics and chemistry. A practical understanding of attosecond optics requires significant background information and foundational theory to make full use of these cutting-edge lasers and advance the technology toward the next generation of ultrafast lasers. Fundamentals of Attosecond Optics provides the first focused introduction to the field. The author presents the underlying concepts and techniques required to enter the field, as well as recent research advances th

  14. Fundamentals of calculus

    CERN Document Server

    Morris, Carla C

    2015-01-01

    Fundamentals of Calculus encourages students to use power, quotient, and product rules for solutions as well as stresses the importance of modeling skills.  In addition to core integral and differential calculus coverage, the book features finite calculus, which lends itself to modeling and spreadsheets.  Specifically, finite calculus is applied to marginal economic analysis, finance, growth, and decay.  Includes: Linear Equations and FunctionsThe DerivativeUsing the Derivative Exponential and Logarithmic Functions Techniques of DifferentiationIntegral CalculusIntegration TechniquesFunctions

  15. Nanomachines fundamentals and applications

    CERN Document Server

    Wang, Joseph

    2013-01-01

    This first-hand account by one of the pioneers of nanobiotechnology brings together a wealth of valuable material in a single source. It allows fascinating insights into motion at the nanoscale, showing how the proven principles of biological nanomotors are being transferred to artificial nanodevices.As such, the author provides engineers and scientists with the fundamental knowledge surrounding the design and operation of biological and synthetic nanomotors and the latest advances in nanomachines. He addresses such topics as nanoscale propulsions, natural biomotors, molecular-scale machin

  16. Information security fundamentals

    CERN Document Server

    Blackley, John A; Peltier, Justin

    2004-01-01

    Effective security rules and procedures do not exist for their own sake-they are put in place to protect critical assets, thereby supporting overall business objectives. Recognizing security as a business enabler is the first step in building a successful program.Information Security Fundamentals allows future security professionals to gain a solid understanding of the foundations of the field and the entire range of issues that practitioners must address. This book enables students to understand the key elements that comprise a successful information security program and eventually apply thes

  17. Fundamentals of engineering electromagnetism

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Nam; Yoon, Youngro; Jun, Sukhee; Jun, Hoin

    2004-08-15

    It indicates fundamentals of engineering electromagnetism. It mentions electromagnetic field model of introduction and International system of units and universal constant, Vector analysis with summary and orthogonal coordinate systems, electrostatic field on Coulomb's law and Gauss's law, electrostatic energy and strength, steady state current with Ohm's law and Joule's law and calculation of resistance, crystallite field with Vector's electrostatic potential, Biot-Savart law and application and Magnetic Dipole, time-Savart and Maxwell equation with potential function and Faraday law of electromagnetic induction, plane electromagnetic wave, transmission line, a wave guide and cavity resonator and antenna arrangement.

  18. Fundamentals of Cavitation

    CERN Document Server

    Franc, Jean-Pierre

    2005-01-01

    The present book is aimed at providing a comprehensive presentation of cavitation phenomena in liquid flows. It is further backed up by the experience, both experimental and theoretical, of the authors whose expertise has been internationally recognized. A special effort is made to place the various methods of investigation in strong relation with the fundamental physics of cavitation, enabling the reader to treat specific problems independently. Furthermore, it is hoped that a better knowledge of the cavitation phenomenon will allow engineers to create systems using it positively. Examples in the literature show the feasibility of this approach.

  19. El grupo fundamental

    Directory of Open Access Journals (Sweden)

    Carlos A. Robles Corbalá

    2015-12-01

    Full Text Available En este artículo se aborda un problema clásico para poder detectar si dos espacios topológicos son homeomorfos o no. Para lo cual a cada espacio topológico se le asocia un grupo algebraico, de tal suerte que si los espacios son homeomorfos, entonces los grupos asociados serán isomorfos. Se presenta una construcción del grupo fundamental de un espacio topológico y se enfoca en demostrar que efectivamente es un grupo.

  20. Fundamentals of Space Systems

    Science.gov (United States)

    Pisacane, Vincent L.

    2005-06-01

    Fundamentals of Space Systems was developed to satisfy two objectives: the first is to provide a text suitable for use in an advanced undergraduate or beginning graduate course in both space systems engineering and space system design. The second is to be a primer and reference book for space professionals wishing to broaden their capabilities to develop, manage the development, or operate space systems. The authors of the individual chapters are practicing engineers that have had extensive experience in developing sophisticated experimental and operational spacecraft systems in addition to having experience teaching the subject material. The text presents the fundamentals of all the subsystems of a spacecraft missions and includes illustrative examples drawn from actual experience to enhance the learning experience. It included a chapter on each of the relevant major disciplines and subsystems including space systems engineering, space environment, astrodynamics, propulsion and flight mechanics, attitude determination and control, power systems, thermal control, configuration management and structures, communications, command and telemetry, data processing, embedded flight software, survuvability and reliability, integration and test, mission operations, and the initial conceptual design of a typical small spacecraft mission.

  1. Testing Our Fundamental Assumptions

    Science.gov (United States)

    Kohler, Susanna

    2016-06-01

    Science is all about testing the things we take for granted including some of the most fundamental aspects of how we understand our universe. Is the speed of light in a vacuum the same for all photons regardless of their energy? Is the rest mass of a photon actually zero? A series of recent studies explore the possibility of using transient astrophysical sources for tests!Explaining Different Arrival TimesArtists illustration of a gamma-ray burst, another extragalactic transient, in a star-forming region. [NASA/Swift/Mary Pat Hrybyk-Keith and John Jones]Suppose you observe a distant transient astrophysical source like a gamma-ray burst, or a flare from an active nucleus and two photons of different energies arrive at your telescope at different times. This difference in arrival times could be due to several different factors, depending on how deeply you want to question some of our fundamental assumptions about physics:Intrinsic delayThe photons may simply have been emitted at two different times by the astrophysical source.Delay due to Lorentz invariance violationPerhaps the assumption that all massless particles (even two photons with different energies) move at the exact same velocity in a vacuum is incorrect.Special-relativistic delayMaybe there is a universal speed for massless particles, but the assumption that photons have zero rest mass is wrong. This, too, would cause photon velocities to be energy-dependent.Delay due to gravitational potentialPerhaps our understanding of the gravitational potential that the photons experience as they travel is incorrect, also causing different flight times for photons of different energies. This would mean that Einsteins equivalence principle, a fundamental tenet of general relativity (GR), is incorrect.If we now turn this problem around, then by measuring the arrival time delay between photons of different energies from various astrophysical sources the further away, the better we can provide constraints on these

  2. The MOND Fundamental Plane

    CERN Document Server

    Cardone, V F; Diaferio, A; Tortora, C; Molinaro, R

    2010-01-01

    Modified Newtonian Dynamics (MOND) has been shown to be able to fit spiral galaxy rotation curves as well as giving a theoretical foundation for empirically determined scaling relations, such as the Tully - Fisher law, without the need for a dark matter halo. As a complementary analysis, one should investigate whether MOND can also reproduce the dynamics of early - type galaxies (ETGs) without dark matter. As a first step, we here show that MOND can indeed fit the observed central velocity dispersion $\\sigma_0$ of a large sample of ETGs assuming a simple MOND interpolating functions and constant anisotropy. We also show that, under some assumptions on the luminosity dependence of the Sersic n parameter and the stellar M/L ratio, MOND predicts a fundamental plane for ETGs : a log - linear relation among the effective radius $R_{eff}$, $\\sigma_0$ and the mean effective intensity $\\langle I_e \\rangle$. However, we predict a tilt between the observed and the MOND fundamental planes.

  3. Fundamentals of Structural Engineering

    CERN Document Server

    Connor, Jerome J

    2013-01-01

    Fundamentals of Structural Engineering provides a balanced, seamless treatment of both classic, analytic methods and contemporary, computer-based techniques for conceptualizing and designing a structure. The book’s principle goal is to foster an intuitive understanding of structural behavior based on problem solving experience for students of civil engineering and architecture who have been exposed to the basic concepts of engineering mechanics and mechanics of materials. Making it distinct from many other undergraduate textbooks, the authors of this text recognize the notion that engineers reason about behavior using simple models and intuition they acquire through problem solving. The approach adopted in this text develops this type of intuition  by presenting extensive, realistic problems and case studies together with computer simulation, which allows rapid exploration of  how a structure responds to changes in geometry and physical parameters. This book also: Emphasizes problem-based understanding of...

  4. Fundamentals of phosphors

    CERN Document Server

    Yen, William M; Yamamoto, Hajime

    2006-01-01

    Drawing from the second edition of the best-selling Handbook of Phosphors, Fundamentals of Phosphors covers the principles and mechanisms of luminescence in detail and surveys the primary phosphor materials as well as their optical properties. The book addresses cutting-edge developments in phosphor science and technology including oxynitride phosphors and the impact of lanthanide level location on phosphor performance.Beginning with an explanation of the physics underlying luminescence mechanisms in solids, the book goes on to interpret various luminescence phenomena in inorganic and organic materials. This includes the interpretation of the luminescence of recently developed low-dimensional systems, such as quantum wells and dots. The book also discusses the excitation mechanisms by cathode-ray and ionizing radiation and by electric fields to produce electroluminescence. The book classifies phosphor materials according to the type of luminescence centers employed or the class of host materials used and inte...

  5. Automotive electronics design fundamentals

    CERN Document Server

    Zaman, Najamuz

    2015-01-01

    This book explains the topology behind automotive electronics architectures and examines how they can be profoundly augmented with embedded controllers. These controllers serve as the core building blocks of today’s vehicle electronics. Rather than simply teaching electrical basics, this unique resource focuses on the fundamental concepts of vehicle electronics architecture, and details the wide variety of Electronic Control Modules (ECMs) that enable the increasingly sophisticated "bells & whistles" of modern designs.  A must-have for automotive design engineers, technicians working in automotive electronics repair centers and students taking automotive electronics courses, this guide bridges the gap between academic instruction and industry practice with clear, concise advice on how to design and optimize automotive electronics with embedded controllers.

  6. Fundamentals of quantum mechanics

    CERN Document Server

    House, J E

    2017-01-01

    Fundamentals of Quantum Mechanics, Third Edition is a clear and detailed introduction to quantum mechanics and its applications in chemistry and physics. All required math is clearly explained, including intermediate steps in derivations, and concise review of the math is included in the text at appropriate points. Most of the elementary quantum mechanical models-including particles in boxes, rigid rotor, harmonic oscillator, barrier penetration, hydrogen atom-are clearly and completely presented. Applications of these models to selected “real world” topics are also included. This new edition includes many new topics such as band theory and heat capacity of solids, spectroscopy of molecules and complexes (including applications to ligand field theory), and small molecules of astrophysical interest.

  7. Lasers Fundamentals and Applications

    CERN Document Server

    Thyagarajan, K

    2010-01-01

    Lasers: Fundamentals and Applications, serves as a vital textbook to accompany undergraduate and graduate courses on lasers and their applications. Ever since their invention in 1960, lasers have assumed tremendous importance in the fields of science, engineering and technology because of their diverse uses in basic research and countless technological applications. This book provides a coherent presentation of the basic physics behind the way lasers work, and presents some of their most important applications in vivid detail. After reading this book, students will understand how to apply the concepts found within to practical, tangible situations. This textbook includes worked-out examples and exercises to enhance understanding, and the preface shows lecturers how to most beneficially match the textbook with their course curricula. The book includes several recent Nobel Lectures, which will further expose students to the emerging applications and excitement of working with lasers. Students who study lasers, ...

  8. Digital Fourier analysis fundamentals

    CERN Document Server

    Kido, Ken'iti

    2015-01-01

    This textbook is a thorough, accessible introduction to digital Fourier analysis for undergraduate students in the sciences. Beginning with the principles of sine/cosine decomposition, the reader walks through the principles of discrete Fourier analysis before reaching the cornerstone of signal processing: the Fast Fourier Transform. Saturated with clear, coherent illustrations, "Digital Fourier Analysis - Fundamentals" includes practice problems and thorough Appendices for the advanced reader. As a special feature, the book includes interactive applets (available online) that mirror the illustrations.  These user-friendly applets animate concepts interactively, allowing the user to experiment with the underlying mathematics. For example, a real sine signal can be treated as a sum of clockwise and counter-clockwise rotating vectors. The applet illustration included with the book animates the rotating vectors and the resulting sine signal. By changing parameters such as amplitude and frequency, the reader ca...

  9. Superconductivity fundamentals and applications

    CERN Document Server

    Buckel, Werner

    2004-01-01

    This is the second English edition of what has become one of the definitive works on superconductivity in German -- currently in its sixth edition. Comprehensive and easy to understand, this introductory text is written especially with the non-specialist in mind. The authors, both long-term experts in this field, present the fundamental considerations without the need for extensive mathematics, describing the various phenomena connected with the superconducting state, with liberal insertion of experimental facts and examples for modern applications. While all fields of superconducting phenomena are dealt with in detail, this new edition pays particular attention to the groundbreaking discovery of magnesium diboride and the current developments in this field. In addition, a new chapter provides an overview of the elements, alloys and compounds where superconductivity has been observed in experiments, together with their major characteristics. The chapter on technical applications has been considerably expanded...

  10. Fundamental partial compositeness

    CERN Document Server

    Sannino, Francesco

    2016-01-01

    We construct renormalizable Standard Model extensions, valid up to the Planck scale, that give a composite Higgs from a new fundamental strong force acting on fermions and scalars. Yukawa interactions of these particles with Standard Model fermions realize the partial compositeness scenario. Successful models exist because gauge quantum numbers of Standard Model fermions admit a minimal enough 'square root'. Furthermore, right-handed SM fermions have an SU(2)$_R$-like structure, yielding a custodially-protected composite Higgs. Baryon and lepton numbers arise accidentally. Standard Model fermions acquire mass at tree level, while the Higgs potential and flavor violations are generated by quantum corrections. We further discuss accidental symmetries and other dynamical features stemming from the new strongly interacting scalars. If the same phenomenology can be obtained from models without our elementary scalars, they would reappear as composite states.

  11. Fundamentals of sustainable neighbourhoods

    CERN Document Server

    Friedman, Avi

    2015-01-01

    This book introduces architects, engineers, builders, and urban planners to a range of design principles of sustainable communities and illustrates them with outstanding case studies. Drawing on the author’s experience as well as local and international case studies, Fundamentals of Sustainable Neighbourhoods presents planning concepts that minimize developments' carbon footprint through compact communities, adaptable and expandable dwellings, adaptable landscapes, and smaller-sized yet quality-designed housing. This book also: Examines in-depth global strategies for minimizing the residential carbon footprint, including district heating, passive solar gain, net-zero residences, as well as preserving the communities' natural assets Reconsiders conceptual approaches in building design and urban planning to promote a better connection between communities and nature Demonstrates practical applications of green architecture Focuses on innovative living spaces in urban environments

  12. Fundamentals of Fire Phenomena

    DEFF Research Database (Denmark)

    Quintiere, James

    discipline. It covers thermo chemistry including mixtures and chemical reactions; Introduces combustion to the fire protection student; Discusses premixed flames and spontaneous ignition; Presents conservation laws for control volumes, including the effects of fire; Describes the theoretical bases...... analyses. Fire phenomena encompass everything about the scientific principles behind fire behaviour. Combining the principles of chemistry, physics, heat and mass transfer, and fluid dynamics necessary to understand the fundamentals of fire phenomena, this book integrates the subject into a clear...... for empirical aspects of the subject of fire; Analyses ignition of liquids and the importance of evaporation including heat and mass transfer; Features the stages of fire in compartments, and the role of scale modelling in fire. The book is written by Prof. James G. Quintiere from University of Maryland...

  13. Peridynamics as a rigorous coarse-graining of atomistics for multiscale materials design.

    Energy Technology Data Exchange (ETDEWEB)

    Lehoucq, Richard B.; Aidun, John Bahram; Silling, Stewart Andrew; Sears, Mark P.; Kamm, James R.; Parks, Michael L.

    2010-09-01

    This report summarizes activities undertaken during FY08-FY10 for the LDRD Peridynamics as a Rigorous Coarse-Graining of Atomistics for Multiscale Materials Design. The goal of our project was to develop a coarse-graining of finite temperature molecular dynamics (MD) that successfully transitions from statistical mechanics to continuum mechanics. The goal of our project is to develop a coarse-graining of finite temperature molecular dynamics (MD) that successfully transitions from statistical mechanics to continuum mechanics. Our coarse-graining overcomes the intrinsic limitation of coupling atomistics with classical continuum mechanics via the FEM (finite element method), SPH (smoothed particle hydrodynamics), or MPM (material point method); namely, that classical continuum mechanics assumes a local force interaction that is incompatible with the nonlocal force model of atomistic methods. Therefore FEM, SPH, and MPM inherit this limitation. This seemingly innocuous dichotomy has far reaching consequences; for example, classical continuum mechanics cannot resolve the short wavelength behavior associated with atomistics. Other consequences include spurious forces, invalid phonon dispersion relationships, and irreconcilable descriptions/treatments of temperature. We propose a statistically based coarse-graining of atomistics via peridynamics and so develop a first of a kind mesoscopic capability to enable consistent, thermodynamically sound, atomistic-to-continuum (AtC) multiscale material simulation. Peridynamics (PD) is a microcontinuum theory that assumes nonlocal forces for describing long-range material interaction. The force interactions occurring at finite distances are naturally accounted for in PD. Moreover, PDs nonlocal force model is entirely consistent with those used by atomistics methods, in stark contrast to classical continuum mechanics. Hence, PD can be employed for mesoscopic phenomena that are beyond the realms of classical continuum mechanics and

  14. Atomistic Mechanisms for Viscoelastic Damping in Inorganic Solids

    Science.gov (United States)

    Ranganathan, Raghavan

    Viscoelasticity, a ubiquitous material property, can be tuned to engineer a wide range of fascinating applications such as mechanical dampers, artificial tissues, functional foams and optoelectronics, among others. Traditionally, soft matter such as polymers and polymer composites have been used extensively for viscoelastic damping applications, owing to the inherent viscous nature of interactions between polymer chains. Although this leads to good damping characteristics, the stiffness in these materials is low, which in turn leads to limitations. In this context, hard inorganic materials and composites are promising candidates for enhanced damping, owing to their large stiffness and, in some cases large loss modulus. Viscoelasticity in these materials has been relatively unexplored and atomistic mechanisms responsible for damping are not apparent. Therefore, the overarching goal of this work is to understand mechanisms for viscoelastic damping in various classes of inorganic composites and alloys at an atomistic level from molecular dynamics simulations. We show that oscillatory shear deformation serves as a powerful probe to explain mechanisms for exceptional damping in hitherto unexplored systems. The first class of inorganic materials consists of crystalline phases of a stiff inclusion in a soft matrix. The two crystals within the composite, namely the soft and a stiff phase, individually show a highly elastic behavior and a very small loss modulus. On the other hand, a composite with the two phases is seen to exhibit damping that is about 20 times larger than predicted theoretical bounds. The primary reason for the damping is due to large anharmonicity in phonon-phonon coupling, resulting from the composite microstructure. A concomitant effect is the distribution of shear strain, which is observed to be highly inhomogeneous and mostly concentrated in the soft phase. Interestingly, the shear frequency at which the damping is greatest is observed to scale with

  15. Atomistic study of the buckling of gold nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Olsson, Paer A.T., E-mail: par.olsson@mek.lth.se [Division of Mechanics, Lund University, PO Box 118, SE-221 00 Lund (Sweden); Park, Harold S., E-mail: parkhs@bu.edu [Department of Mechanical Engineering, Boston University, Boston, MA 02215 (United States)

    2011-06-15

    In this work, we present results from atomistic simulations of gold nanowires under axial compression, with a focus on examining the effects of both axial and surface orientation effects on the buckling behavior. This was accomplished by using molecular statics simulations while considering three different crystallographic systems: <1 0 0>/{l_brace}1 0 0{r_brace}, <1 0 0>/{l_brace}1 1 0{r_brace} and <1 1 0>/{l_brace}1 1 0{r_brace}{l_brace}1 0 0{r_brace}, with aspect ratios spanning from 20 to 50 and cross-sectional dimensions ranging from 2.45 to 5.91 nm. The simulations indicate that there is a deviation from the inverse square length dependence of critical forces predicted from traditional linear elastic Bernoulli-Euler and Timoshenko beam theories, where the nature of the deviation from the perfect inverse square length behavior differs for different crystallographic systems. This variation is found to be strongly correlated to either stiffening or increased compliance of the tangential stiffness due to the influence of nonlinear elasticity, which leads to normalized critical forces that decrease with decreasing aspect ratio for the <1 0 0>/{l_brace}1 0 0{r_brace} and <1 0 0>/{l_brace}1 1 0{r_brace} systems, but increase with decreasing aspect ratio for the <1 1 0>/{l_brace}1 1 0{r_brace}{l_brace}1 0 0{r_brace} system. In contrast, it was found that the critical strains are all lower than their bulk counterparts, and that the critical strains decrease with decreasing cross-sectional dimensions; the lower strains may be an effect emanating from the presence of the surfaces, which are all more elastically compliant than the bulk and thus give rise to a more compliant flexural rigidity.

  16. Linking Atomistic and Mesoscale Simulations of Water Soluble Polymers

    Science.gov (United States)

    Jones, J. L.

    2003-03-01

    There exist a range of techniques for studying surfactants and polymers in the mesoscale regime. One of the challenges is to link mesoscale theories and simulations to other calculation methods which address different length scales of the system. We introduce some mesoscale methods of calculation for polymers and surfactants and then present a case study of where mesoscale modelling is used for mechanistic understanding, by linking the method to high throughput in-silico screening methods. We look at the adsorption onto silica of ethylene oxide (EO)/ propylene oxide (PO) block copolymers (lutrols) which have been modified by end-grafting of short, cationic dimethylamino ethyl methacrylate (DMAEMA)chains. Given that the silica surface is negatively charged, it is remarkable that in some circumstances, polymers with longercationic chains have a lower adsorption. The effect is attributed to a competition between strong adsorption of the cationic DMAEMA groups driven by electrostatics, and weaker adsorption of the more numerous EO groups. This then raises the question of how we produce the values for the mesoscale parameters in these models and in the second part of the talk we describe a calculation method for doing this for water soluble polymers. The most promising route, but notoriously costly, is based on free energy calculations at the atomistic level. Free energy calculations are computationally intensive in general, but in an aqueous system one is also faced with the additional problem of using complex continuum models and/or accurate interaction potentials for water. Here we show how potential of mean force (PMF)calculations offer a practical alternative which avoids these drawbacks, though one is still faced with extremely long simulations.

  17. Megasonic cleaning, cavitation, and substrate damage: an atomistic approach

    Science.gov (United States)

    Kapila, Vivek; Deymier, Pierre A.; Shende, Hrishikesh; Pandit, Viraj; Raghavan, Srini; Eschbach, Florence O.

    2006-05-01

    Megasonic cleaning has been a traditional approach for the cleaning of photomasks. Its feasibility as a damage free approach to sub 50 nm particulate removal is under investigation for the cleaning of optical and EUV photomasks. Two major mechanisms are active in a megasonic system, namely, acoustic streaming and acoustic cavitation. Acoustic streaming is instrumental in contaminant removal via application of drag force and rolling of particles, while cavitation may dislodge particles by the release of large energy during cavity implosion or by acting as a secondary source of microstreaming. Often times, the structures (substrates with or without patterns) subjected to megasonic cleaning show evidence of damage. This is one of the impediments in the implementation of megasonic technology for 45 nm and future technology nodes. Prior work suggests that acoustic streaming does not lead to sufficiently strong forces to cause damage to the substrates or patterns. However, current knowledge of the effects of cavitation on cleaning and damage can be described, at best, as speculative. Recent experiments suggest existence of a cavity size and energy distributions in megasonic systems that may be responsible for cleaning and damage. In the current work, we develop a two-dimensional atomistic model to study such multibubble cavitation phenomena. The model consists of a Lennard-Jones liquid which is subjected to sinusoidal pressure changes leading to the formation of cavitation bubbles. The current work reports on the effects of pressure amplitude (megasonic power) and frequency on cavity size distributions in vaporous and gaseous cavitation. The findings of the work highlight the role of multibubble cavitation as cleaning and damage mechanism in megasonic cleaning.

  18. A fully atomistic model of the Cx32 connexon.

    Directory of Open Access Journals (Sweden)

    Sergio Pantano

    Full Text Available Connexins are plasma membrane proteins that associate in hexameric complexes to form channels named connexons. Two connexons in neighboring cells may dock to form a "gap junction" channel, i.e. an intercellular conduit that permits the direct exchange of solutes between the cytoplasm of adjacent cells and thus mediate cell-cell ion and metabolic signaling. The lack of high resolution data for connexon structures has hampered so far the study of the structure-function relationships that link molecular effects of disease-causing mutations with their observed phenotypes. Here we present a combination of modeling techniques and molecular dynamics (MD to infer side chain positions starting from low resolution structures containing only C alpha atoms. We validated this procedure on the structure of the KcsA potassium channel, which is solved at atomic resolution. We then produced a fully atomistic model of a homotypic Cx32 connexon starting from a published model of the C alpha carbons arrangement for the connexin transmembrane helices, to which we added extracellular and cytoplasmic loops. To achieve structural relaxation within a realistic environment, we used MD simulations inserted in an explicit solvent-membrane context and we subsequently checked predictions of putative side chain positions and interactions in the Cx32 connexon against a vast body of experimental reports. Our results provide new mechanistic insights into the effects of numerous spontaneous mutations and their implication in connexin-related pathologies. This model constitutes a step forward towards a structurally detailed description of the gap junction architecture and provides a structural platform to plan new biochemical and biophysical experiments aimed at elucidating the structure of connexin channels and hemichannels.

  19. AIDS.gov

    Science.gov (United States)

    ... concerns. Search Services Share This Help National HIV/AIDS Strategy Check out NHAS's latest progress in the ... from AIDS.gov Read more AIDS.gov tweets AIDS.gov HIV/AIDS Basics • Federal Resources • Using New ...

  20. Aids for Handicapped Readers.

    Science.gov (United States)

    Library of Congress, Washington, DC. Div. for the Blind and Physically Handicapped.

    The reference circular provides information on approximately 50 reading and writing aids intended for physically or visually handicapped individuals. Described are low vision aids, aids for holding a book or turning pages, aids for reading in bed, handwriting aids, typewriters and accessories, braille writing equipment, sound reproducers, and aids…

  1. Fundamentals of ergonomic exoskeleton robots

    NARCIS (Netherlands)

    Schiele, A.

    2008-01-01

    This thesis is the first to provide the fundamentals of ergonomic exoskeleton design. The fundamental theory as well as technology necessary to analyze and develop ergonomic wearable robots interacting with humans is established and validated by experiments and prototypes. The fundamentals are (1) a

  2. Nonadiabatic Dynamics in Atomistic Environments: Harnessing Quantum-Classical Theory with Generalized Quantum Master Equations.

    Science.gov (United States)

    Pfalzgraff, William C; Kelly, Aaron; Markland, Thomas E

    2015-12-03

    The development of methods that can efficiently and accurately treat nonadiabatic dynamics in quantum systems coupled to arbitrary atomistic environments remains a significant challenge in problems ranging from exciton transport in photovoltaic materials to electron and proton transfer in catalysis. Here we show that our recently introduced MF-GQME approach, which combines Ehrenfest mean field theory with the generalized quantum master equation framework, is able to yield quantitative accuracy over a wide range of charge-transfer regimes in fully atomistic environments. This is accompanied by computational speed-ups of up to 3 orders of magnitude over a direct application of Ehrenfest theory. This development offers the opportunity to efficiently investigate the atomistic details of nonadiabatic quantum relaxation processes in regimes where obtaining accurate results has previously been elusive.

  3. Accelerating a hybrid continuum-atomistic fluidic model with on-the-fly machine learning

    CERN Document Server

    Stephenson, David; Lockerby, Duncan A

    2016-01-01

    We present a hybrid continuum-atomistic scheme which combines molecular dynamics (MD) simulations with on-the-fly machine learning techniques for the accurate and efficient prediction of multiscale fluidic systems. By using a Gaussian process as a surrogate model for the computationally expensive MD simulations, we use Bayesian inference to predict the system behaviour at the atomistic scale, purely by consideration of the macroscopic inputs and outputs. Whenever the uncertainty of this prediction is greater than a predetermined acceptable threshold, a new MD simulation is performed to continually augment the database, which is never required to be complete. This provides a substantial enhancement to the current generation of hybrid methods, which often require many similar atomistic simulations to be performed, discarding information after it is used once. We apply our hybrid scheme to nano-confined unsteady flow through a high-aspect-ratio converging-diverging channel, and make comparisons between the new s...

  4. An atomistic modelling of the porosity impact on UO{sub 2} matrix macroscopic properties

    Energy Technology Data Exchange (ETDEWEB)

    Jelea, A., E-mail: andrei.jelea@irsn.fr [Institut de Radioprotection et de Surete Nucleaire (IRSN), DPAM, SEMCA, LEC, Cadarache (France); Centre Interdisciplinaire des Nanosciences de Marseille, CNRS, Campus de Luminy, Marseille 13288 (France); Institute of Physical Chemistry Ilie Murgulescu, Romanian Academy, 202 Spl Independentei St., 060021 Bucharest-12 (Romania); Colbert, M. [Institut de Radioprotection et de Surete Nucleaire (IRSN), DPAM, SEMCA, LEC, Cadarache (France); Centre Interdisciplinaire des Nanosciences de Marseille, CNRS, Campus de Luminy, Marseille 13288 (France); Ribeiro, F. [Institut de Radioprotection et de Surete Nucleaire (IRSN), DPAM, SEMCA, LEC, Cadarache (France); Treglia, G. [Centre Interdisciplinaire des Nanosciences de Marseille, CNRS, Campus de Luminy, Marseille 13288 (France); Pellenq, R.J.-M. [Centre Interdisciplinaire des Nanosciences de Marseille, CNRS, Campus de Luminy, Marseille 13288 (France); Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)

    2011-08-15

    Highlights: > The porosity impact on the UO{sub 2} matrix thermomechanical properties was investigated. > Atomistic simulation techniques were used in this study. > The UO{sub 2} thermal expansion coefficient is modified due to the pore surface effects. > The elastic moduli at 0 K and at finite temperature decrease linearly with porosity. - Abstract: The porosity impact on the UO{sub 2} matrix thermomechanical properties was investigated using atomistic simulation techniques. The porosity modifies the thermal expansion coefficient and this is attributed to pore surface effects. The elastic moduli at 0 K and at finite temperature decrease with porosity, this variation being well approximated using affine functions. These results agree with other mesoscale model predictions and experimental data, showing the ability of the semiempirical potential atomistic simulations to give an overall good description of the porous UO{sub 2}. However, the surface effects are incompletely described.

  5. Atomistic simulation of nanoporous layered double hydroxide materials and their properties. I. Structural modeling

    Science.gov (United States)

    Kim, Nayong; Kim, Yongman; Tsotsis, Theodore T.; Sahimi, Muhammad

    2005-06-01

    An atomistic model of layered double hydroxides, an important class of nanoporous materials, is presented. These materials have wide applications, ranging from adsorbents for gases and liquid ions to nanoporous membranes and catalysts. They consist of two types of metallic cations that are accommodated by a close-packed configuration of OH- and other anions in a positively charged brucitelike layer. Water and various anions are distributed in the interlayer space for charge compensation. A modified form of the consistent-valence force field, together with energy minimization and molecular dynamics simulations, is utilized for developing an atomistic model of the materials. To test the accuracy of the model, we compare the vibrational frequencies, x-ray diffraction patterns, and the basal spacing of the material, computed using the atomistic model, with our experimental data over a wide range of temperature. Good agreement is found between the computed and measured quantities.

  6. Origin of unrealistic blunting during atomistic fracture simulations based on MEAM potentials

    Science.gov (United States)

    Ko, Won-Seok; Lee, Byeong-Joo

    2014-06-01

    Atomistic simulations based on interatomic potentials have frequently failed to correctly reproduce the brittle fracture of materials, showing an unrealistic blunting. We analyse the origin of the unrealistic blunting during atomistic simulations by modified embedded-atom method (MEAM) potentials for experimentally well-known brittle materials such as bcc tungsten and diamond silicon. The radial cut-off which has been thought to give no influence on MEAM calculations is found to have a decisive effect on the crack propagation behaviour. Extending both cut-off distance and truncation range can prevent the unrealistic blunting, reproducing many well-known fracture behaviour which have been difficult to reproduce. The result provides a guideline for future atomistic simulations that focus on various fracture-related phenomena including the failure of metallic-covalent bonding material systems using MEAM potentials.

  7. Revisiting energy efficiency fundamentals

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Lombard, L.; Velazquez, D. [Grupo de Termotecnia, Escuela Superior de Ingenieros, Universidad de Sevilla, Camino de los Descubrimientos s/n, 41092 Seville (Spain); Ortiz, J. [Building Research Establishment (BRE), Garston, Watford, WD25 9XX (United Kingdom)

    2013-05-15

    Energy efficiency is a central target for energy policy and a keystone to mitigate climate change and to achieve a sustainable development. Although great efforts have been carried out during the last four decades to investigate the issue, focusing into measuring energy efficiency, understanding its trends and impacts on energy consumption and to design effective energy efficiency policies, many energy efficiency-related concepts, some methodological problems for the construction of energy efficiency indicators (EEI) and even some of the energy efficiency potential gains are often ignored or misunderstood, causing no little confusion and controversy not only for laymen but even for specialists. This paper aims to revisit, analyse and discuss some efficiency fundamental topics that could improve understanding and critical judgement of efficiency stakeholders and that could help in avoiding unfounded judgements and misleading statements. Firstly, we address the problem of measuring energy efficiency both in qualitative and quantitative terms. Secondly, main methodological problems standing in the way of the construction of EEI are discussed, and a sequence of actions is proposed to tackle them in an ordered fashion. Finally, two key topics are discussed in detail: the links between energy efficiency and energy savings, and the border between energy efficiency improvement and renewable sources promotion.

  8. Fundamental Limits of Cooperation

    CERN Document Server

    Lozano, Angel; Andrews, Jeffrey G

    2012-01-01

    Cooperation is viewed as a key ingredient for interference management in wireless systems. This paper shows that cooperation has fundamental limitations. The main result is that even full cooperation between transmitters cannot in general change an interference-limited network to a noise-limited network. The key idea is that there exists a spectral efficiency upper bound that is independent of the transmit power. First, a spectral efficiency upper bound is established for systems that rely on pilot-assisted channel estimation; in this framework, cooperation is shown to be possible only within clusters of limited size, which are subject to out-of-cluster interference whose power scales with that of the in-cluster signals. Second, an upper bound is also shown to exist when cooperation is through noncoherent communication; thus, the spectral efficiency limitation is not a by-product of the reliance on pilot-assisted channel estimation. Consequently, existing literature that routinely assumes the high-power spect...

  9. GRBs and Fundamental Physics

    Science.gov (United States)

    Petitjean, Patrick; Wang, F. Y.; Wu, X. F.; Wei, J. J.

    2016-12-01

    Gamma-ray bursts (GRBs) are short and intense flashes at the cosmological distances, which are the most luminous explosions in the Universe. The high luminosities of GRBs make them detectable out to the edge of the visible universe. So, they are unique tools to probe the properties of high-redshift universe: including the cosmic expansion and dark energy, star formation rate, the reionization epoch and the metal evolution of the Universe. First, they can be used to constrain the history of cosmic acceleration and the evolution of dark energy in a redshift range hardly achievable by other cosmological probes. Second, long GRBs are believed to be formed by collapse of massive stars. So they can be used to derive the high-redshift star formation rate, which can not be probed by current observations. Moreover, the use of GRBs as cosmological tools could unveil the reionization history and metal evolution of the Universe, the intergalactic medium (IGM) properties and the nature of first stars in the early universe. But beyond that, the GRB high-energy photons can be applied to constrain Lorentz invariance violation (LIV) and to test Einstein's Equivalence Principle (EEP). In this paper, we review the progress on the GRB cosmology and fundamental physics probed by GRBs.

  10. Fundamentals of klystron testing

    Energy Technology Data Exchange (ETDEWEB)

    Caldwell, J.W. Jr.

    1978-08-01

    Fundamentals of klystron testing is a text primarily intended for the indoctrination of new klystron group test stand operators. It should significantly reduce the familiarization time of a new operator, making him an asset to the group sooner than has been experienced in the past. The new employee must appreciate the mission of SLAC before he can rightfully be expected to make a meaningful contribution to the group's effort. Thus, the introductory section acquaints the reader with basic concepts of accelerators in general, then briefly describes major physical aspects of the Stanford Linear Accelerator. Only then is his attention directed to the klystron, with its auxiliary systems, and the rudiments of klystron tube performance checks. It is presumed that the reader is acquainted with basic principles of electronics and scientific notation. However, to preserve the integrity of an indoctrination guide, tedious technical discussions and mathematical analysis have been studiously avoided. It is hoped that the new operator will continue to use the text for reference long after his indoctrination period is completed. Even the more experienced operator should find that particular sections will refresh his understanding of basic principles of klystron testing.

  11. Macroeconomic Issues in Foreign Aid

    DEFF Research Database (Denmark)

    Hjertholm, Peter; Laursen, Jytte; White, Howard

    foreign aid, macroeconomics of aid, gap models, aid fungibility, fiscal response models, foreign debt,......foreign aid, macroeconomics of aid, gap models, aid fungibility, fiscal response models, foreign debt,...

  12. Crawling Aid

    Science.gov (United States)

    1982-01-01

    The Institute for the Achievement of Human Potential developed a device known as the Vehicle for Initial Crawling (VIC); the acronym is a tribute to the crawler's inventor, Hubert "Vic" Vykukal; is an effective crawling aid. The VIC is used by brain injured children who are unable to crawl due to the problems of weight-bearing and friction, caused by gravity. It is a rounded plywood frame large enough to support the child's torso, leaving arms and legs free to move. On its underside are three aluminum discs through which air is pumped to create an air-bearing surface that has less friction than a film of oil. Upper side contains the connection to the air supply and a pair of straps which restrain the child and cause the device to move with him. VIC is used with the intent to recreate the normal neurological connection between brain and muscles. Over repetitive use of the device the child develops his arm and leg muscles as well as coordination. Children are given alternating therapy, with and without the VIC until eventually the device is no longer needed.

  13. Analysis of Twisting of Cellulose Nanofibrils in Atomistic Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Paavilainen, S.; Rog, T.; Vattulainen, I.

    2011-01-01

    We use atomistic molecular dynamics simulations to study the crystal structure of cellulose nanofibrils, whose sizes are comparable with the crystalline parts in commercial nanocellulose. The simulations show twisting, whose rate of relaxation is strongly temperature dependent. Meanwhile, no sign......We use atomistic molecular dynamics simulations to study the crystal structure of cellulose nanofibrils, whose sizes are comparable with the crystalline parts in commercial nanocellulose. The simulations show twisting, whose rate of relaxation is strongly temperature dependent. Meanwhile......, no significant bending or stretching of nanocellulose is discovered. Considerations of atomic-scale interaction patterns bring about that the twisting arises from hydrogen bonding within and between the chains in a fibril....

  14. Hypercrosslinked polystyrene networks: An atomistic molecular dynamics simulation combined with a mapping/reverse mapping procedure

    Energy Technology Data Exchange (ETDEWEB)

    Lazutin, A. A.; Glagolev, M. K.; Vasilevskaya, V. V.; Khokhlov, A. R. [A. N. Nesmeyanov Institute of Organoelement Compounds RAS, Vavilova Str. 28, 119991 Moscow (Russian Federation)

    2014-04-07

    An algorithm involving classical molecular dynamics simulations with mapping and reverse mapping procedure is here suggested to simulate the crosslinking of the polystyrene dissolved in dichloroethane by monochlorodimethyl ether. The algorithm comprises consecutive stages: molecular dynamics atomistic simulation of a polystyrene solution, the mapping of atomistic structure onto coarse-grained model, the crosslink formation, the reverse mapping, and finally relaxation of the structure dissolved in dichloroethane and in dry state. The calculated values of the specific volume and the elastic modulus are in reasonable quantitative correspondence with experimental data.

  15. HIV and AIDS

    Science.gov (United States)

    ... Emergency Room? What Happens in the Operating Room? HIV and AIDS KidsHealth > For Kids > HIV and AIDS ... actually the virus that causes the disease AIDS. HIV Hurts the Immune System People who are HIV ...

  16. Heart attack first aid

    Science.gov (United States)

    First aid - heart attack; First aid - cardiopulmonary arrest; First aid - cardiac arrest ... A heart attack occurs when the blood flow that carries oxygen to the heart is blocked. The heart muscle ...

  17. Breathing difficulties - first aid

    Science.gov (United States)

    Difficulty breathing - first aid; Dyspnea - first aid; Shortness of breath - first aid ... Breathing difficulty is almost always a medical emergency. An exception is feeling slightly winded from normal activity, ...

  18. Fundamentals of Physics, Extended 7th Edition

    Science.gov (United States)

    Halliday, David; Resnick, Robert; Walker, Jearl

    2004-05-01

    No other book on the market today can match the 30-year success of Halliday, Resnick and Walker's Fundamentals of Physics! Fundamentals of Physics, 7th Edition and the Extended Version, 7th Edition offer a solid understanding of fundamental physics concepts, helping readers apply this conceptual understanding to quantitative problem solving, in a breezy, easy-to-understand style. A unique combination of authoritative content and stimulating applications. * Numerous improvements in the text, based on feedback from the many users of the sixth edition (both instructors and students) * Several thousand end-of-chapter problems have been rewritten to streamline both the presentations and answers * 'Chapter Puzzlers' open each chapter with an intriguing application or question that is explained or answered in the chapter * Problem-solving tactics are provided to help beginning Physics students solve problems and avoid common error * The first section in every chapter introduces the subject of the chapter by asking and answering, "What is Physics?" as the question pertains to the chapter * Numerous supplements available to aid teachers and students The extended edition provides coverage of developments in Physics in the last 100 years, including: Einstein and Relativity, Bohr and others and Quantum Theory, and the more recent theoretical developments like String Theory.

  19. Scalable and portable visualization of large atomistic datasets

    Science.gov (United States)

    Sharma, Ashish; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya

    2004-10-01

    A scalable and portable code named Atomsviewer has been developed to interactively visualize a large atomistic dataset consisting of up to a billion atoms. The code uses a hierarchical view frustum-culling algorithm based on the octree data structure to efficiently remove atoms outside of the user's field-of-view. Probabilistic and depth-based occlusion-culling algorithms then select atoms, which have a high probability of being visible. Finally a multiresolution algorithm is used to render the selected subset of visible atoms at varying levels of detail. Atomsviewer is written in C++ and OpenGL, and it has been tested on a number of architectures including Windows, Macintosh, and SGI. Atomsviewer has been used to visualize tens of millions of atoms on a standard desktop computer and, in its parallel version, up to a billion atoms. Program summaryTitle of program: Atomsviewer Catalogue identifier: ADUM Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUM Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer for which the program is designed and others on which it has been tested: 2.4 GHz Pentium 4/Xeon processor, professional graphics card; Apple G4 (867 MHz)/G5, professional graphics card Operating systems under which the program has been tested: Windows 2000/XP, Mac OS 10.2/10.3, SGI IRIX 6.5 Programming languages used: C++, C and OpenGL Memory required to execute with typical data: 1 gigabyte of RAM High speed storage required: 60 gigabytes No. of lines in the distributed program including test data, etc.: 550 241 No. of bytes in the distributed program including test data, etc.: 6 258 245 Number of bits in a word: Arbitrary Number of processors used: 1 Has the code been vectorized or parallelized: No Distribution format: tar gzip file Nature of physical problem: Scientific visualization of atomic systems Method of solution: Rendering of atoms using computer graphic techniques, culling algorithms for data

  20. Fundamentals of Space Medicine

    Science.gov (United States)

    Clément, Gilles

    2005-03-01

    A total of more than 240 human space flights have been completed to date, involving about 450 astronauts from various countries, for a combined total presence in space of more than 70 years. The seventh long-duration expedition crew is currently in residence aboard the International Space Station, continuing a permanent presence in space that began in October 2000. During that time, investigations have been conducted on both humans and animal models to study the bone demineralization and muscle deconditioning, space motion sickness, the causes and possible treatment of postflight orthostatic intolerance, the changes in immune function, crew and crew-ground interactions, and the medical issues of living in a space environment, such as the effects of radiation or the risk of developing kidney stones. Some results of these investigations have led to fundamental discoveries about the adaptation of the human body to the space environment. Gilles Clément has been active in this research. This readable text presents the findings from the life science experiments conducted during and after space missions. Topics discussed in this book include: adaptation of sensory-motor, cardio-vascular, bone, and muscle systems to the microgravity of spaceflight; psychological and sociological issues of living in a confined, isolated, and stressful environment; operational space medicine, such as crew selection, training and in-flight health monitoring, countermeasures and support; results of space biology experiments on individual cells, plants, and animal models; and the impact of long-duration missions such as the human mission to Mars. The author also provides a detailed description of how to fly a space experiment, based on his own experience with research projects conducted onboard Salyut-7, Mir, Spacelab, and the Space Shuttle. Now is the time to look at the future of human spaceflight and what comes next. The future human exploration of Mars captures the imagination of both the

  1. Maximum Entropy Fundamentals

    Directory of Open Access Journals (Sweden)

    F. Topsøe

    2001-09-01

    Full Text Available Abstract: In its modern formulation, the Maximum Entropy Principle was promoted by E.T. Jaynes, starting in the mid-fifties. The principle dictates that one should look for a distribution, consistent with available information, which maximizes the entropy. However, this principle focuses only on distributions and it appears advantageous to bring information theoretical thinking more prominently into play by also focusing on the "observer" and on coding. This view was brought forward by the second named author in the late seventies and is the view we will follow-up on here. It leads to the consideration of a certain game, the Code Length Game and, via standard game theoretical thinking, to a principle of Game Theoretical Equilibrium. This principle is more basic than the Maximum Entropy Principle in the sense that the search for one type of optimal strategies in the Code Length Game translates directly into the search for distributions with maximum entropy. In the present paper we offer a self-contained and comprehensive treatment of fundamentals of both principles mentioned, based on a study of the Code Length Game. Though new concepts and results are presented, the reading should be instructional and accessible to a rather wide audience, at least if certain mathematical details are left aside at a rst reading. The most frequently studied instance of entropy maximization pertains to the Mean Energy Model which involves a moment constraint related to a given function, here taken to represent "energy". This type of application is very well known from the literature with hundreds of applications pertaining to several different elds and will also here serve as important illustration of the theory. But our approach reaches further, especially regarding the study of continuity properties of the entropy function, and this leads to new results which allow a discussion of models with so-called entropy loss. These results have tempted us to speculate over

  2. Atomistic Method Applied to Computational Modeling of Surface Alloys

    Science.gov (United States)

    Bozzolo, Guillermo H.; Abel, Phillip B.

    2000-01-01

    The formation of surface alloys is a growing research field that, in terms of the surface structure of multicomponent systems, defines the frontier both for experimental and theoretical techniques. Because of the impact that the formation of surface alloys has on surface properties, researchers need reliable methods to predict new surface alloys and to help interpret unknown structures. The structure of surface alloys and when, and even if, they form are largely unpredictable from the known properties of the participating elements. No unified theory or model to date can infer surface alloy structures from the constituents properties or their bulk alloy characteristics. In spite of these severe limitations, a growing catalogue of such systems has been developed during the last decade, and only recently are global theories being advanced to fully understand the phenomenon. None of the methods used in other areas of surface science can properly model even the already known cases. Aware of these limitations, the Computational Materials Group at the NASA Glenn Research Center at Lewis Field has developed a useful, computationally economical, and physically sound methodology to enable the systematic study of surface alloy formation in metals. This tool has been tested successfully on several known systems for which hard experimental evidence exists and has been used to predict ternary surface alloy formation (results to be published: Garces, J.E.; Bozzolo, G.; and Mosca, H.: Atomistic Modeling of Pd/Cu(100) Surface Alloy Formation. Surf. Sci., 2000 (in press); Mosca, H.; Garces J.E.; and Bozzolo, G.: Surface Ternary Alloys of (Cu,Au)/Ni(110). (Accepted for publication in Surf. Sci., 2000.); and Garces, J.E.; Bozzolo, G.; Mosca, H.; and Abel, P.: A New Approach for Atomistic Modeling of Pd/Cu(110) Surface Alloy Formation. (Submitted to Appl. Surf. Sci.)). Ternary alloy formation is a field yet to be fully explored experimentally. The computational tool, which is based on

  3. Atomistic modeling of a KRT35/KRT85 keratin dimer: folding in aqueous solution and unfolding under tensile load.

    Science.gov (United States)

    Duchstein, Patrick; Clark, Tim; Zahn, Dirk

    2015-09-14

    We present an atomistic model of a full KRT35/KRT85 dimer, a fundamental building block of human hair. For both monomers initial structures were generated using empirical tools based on homology considerations, followed by the formulation of a naiïve dimer model from docking the monomers in vacuum. Relaxation in aqueous solution was then explored from molecular dynamics simulation. Driven by hydrophobic segregation and protein-protein hydrogen bonding relaxation dynamics result in a folded dimer arrangement which shows a striking encounter of cystein groups. Our simulations hence suggests that (i) cystein groups in the coil regions of keratin are well suited to establish disulfide bonds between the two monomers that constitute the dimer, and (ii) the particularly large number of cystein groups in the head and tail regions promotes the connection of dimers to establish meso- to macroscale fibers. Moreover, we show the molecular mechanisms of elastic and plastic deformation under tensile load. Upon elongation beyond the elastic regime, unfolding was identified as the exposure of hydrophobic moieties and the breaking of protein-protein hydrogen bonds. Therein, the step-wise character of the series of unfolding events leads to a broad regime of constant force in response to further elongation.

  4. Atomistic insight into adsorption, mobility, and vibration of water in ion-exchanged zeolite-like metal-organic frameworks.

    Science.gov (United States)

    Nalaparaju, A; Babarao, R; Zhao, X S; Jiang, J W

    2009-09-22

    The adsorption, mobility, and vibration of water in ion-exchanged rho-zeolite-like metal-organic frameworks (ZMOFs) are investigated using atomistic simulations. Because of the high affinity for the ionic framework and nonframework ions, water is strongly adsorbed in rho-ZMOFs with a three-step adsorption mechanism. At low pressures, water is preferentially adsorbed onto Na(+) ions, particularly at site II; with increasing pressure, adsorption occurs near the framework and finally in the large cage. Upon water adsorption, Na(+) ions are observed to redistribute from site I to site II and gradually hydrated with increasing pressure. In Li-, Na-, and Cs-exchanged rho-ZMOFs, the adsorption capacity and isosteric heat decrease with increasing ionic radius attributed to the reduced electrostatic interaction and free volume. The mobility of water in Na-rho-ZMOF increases at low pressures but decreases upon approaching saturation. With sufficient amount of water present, the mobility of Na(+) ions is promoted. The vibrational spectra of water in Na-rho-ZMOF exhibit distinct bands for librational motion, bending, and stretching. The librational motion has a frequency higher than bulk water due to confinement. With increasing loading and hence stronger coordinative attraction, the bending frequency shows a blue shift. Symmetric and asymmetric modes are observed in the stretching as a consequence of the strong water-ion interaction. This study provides a fundamental microscopic insight into the static and dynamic properties of water in charged ZMOFs and reveals the subtle interplay between water and nonframework ions.

  5. An atomistic approach to conduction between nanoelectrodes through a single molecule.

    Science.gov (United States)

    Reimers, Jeffrey R; Shapley, Warwick A; Lambropoulos, Nicholas; Hush, Noel S

    2002-04-01

    Capacitance and other properties of nanoelectrodes, finite-size metal clusters envisaged for use in complex molecular-electronic devices, are discussed. The applicability of classical electrostatics (Coulomb's and Gauss' law, Poisson's equation, etc.) to atomistic systems is investigated and the self-energy necessary to store a finite charge on an atom is found to be of central importance. In particular, the neglect of electron exchange is found to introduce severe limitations, with quantum calculations predicting fundamentally different electronic structures. Also, the well-known poor representation of the atomic self-energy inherent to modern DFT is discussed, along with its implications for molecular electronics calculations. An INDO/S method is introduced with new parameters for gold. This is the simplest approximate computational scheme that correctly includes quantum electrostatic, resonance, and spin effects, and is capable of describing arbitrary excited electronic states. Encouraging results are obtained for some trial problems. In particular, voltage differential between the electrodes in electrode-molecule-electrode conduction is obtained, not through an a priori prescription but rather by moving whole electrons between the electrodes and analyzing the response. The voltage drops across the molecule-electrode junctions and the central molecular region are then deduced. This alternative to the current Landauer-based 1-particle transmission equations for electrode-molecule-electrode conduction is discussed in terms of the use of the electronic states of the system. It provides a proper description not only of conduction via electrode-to-molecule charge or hole transfer but also of conduction via simultaneous charge and hole transfer via low-lying excited molecular electronic states, including the ability to account for electroluminescence and other chemical effects. In addition, various aspects of our research on the quantitative prediction of the I

  6. Communication technology update and fundamentals

    CERN Document Server

    Grant, August E

    2010-01-01

    New communication technologies are being introduced at an astonishing rate. Making sense of these technologies is increasingly difficult. Communication Technology Update and Fundamentals is the single best source for the latest developments, trends, and issues in communication technology. Featuring the fundamental framework along with the history and background of communication technologies, Communication Technology Update and Fundamentals, 12th edition helps you stay ahead of these ever-changing and emerging technologies.As always, every chapter ha

  7. Atomistic simulation of laser ablation of gold : Effect of pressure relaxation

    NARCIS (Netherlands)

    Norman, G. E.; Starikov, S. V.; Stegailov, V. V.

    2012-01-01

    The process of ablation of a gold target by femto- and picosecond laser radiation pulses has been studied by numerical simulations using an atomistic model with allowance for the electron subsystem and the dependence of the ion-ion interaction potential on the electron temperature. Using this potent

  8. Software News and Update Reconstruction of Atomistic Details from Coarse-Grained Structures

    NARCIS (Netherlands)

    Rzepiela, Andrzej J.; Schafer, Lars V.; Goga, Nicolae; Risselada, H. Jelger; De Vries, Alex H.; Marrink, Siewert J.

    2010-01-01

    We present an algorithm to reconstruct atomistic structures from their corresponding coarse-grained (CG) representations and its implementation into the freely available molecular dynamics (MD) program package GROMACS. The central part of the algorithm is a simulated annealing MD simulation in which

  9. A Mathematical Analysis of Atomistic-to-Continuum (AtC) Multiscale Coupling Methods

    Energy Technology Data Exchange (ETDEWEB)

    Gunzburger, Max

    2013-11-13

    We have worked on several projects aimed at improving the efficiency and understanding of multiscale methods, especially those applicable to problems involving atomistic-to-continuum coupling. Activities include blending methods for AtC coupling and efficient quasi-continuum methods for problems with long-range interactions.

  10. Atomistic study on the FCC/BCC interface structure with {112}KS orientation

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Keonwook [Los Alamos National Laboratory; Beyerlein, Irene [Los Alamos National Laboratory

    2011-09-23

    In this study, atomistic simulation is used to explore the atomic interface structure, the intrinsic defect network, and mechanism of twin formation from the {112}KS Cu-Nb interface. The interface structure of different material systems AI-Fe and AI-Nb are also compared with Cu-Nb interface.

  11. Hybrid simulations : combining atomistic and coarse-grained force fields using virtual sites

    NARCIS (Netherlands)

    Rzepiela, Andrzej J.; Louhivuori, Martti; Peter, Christine; Marrink, Siewert J.

    2011-01-01

    Hybrid simulations, in which part of the system is represented at atomic resolution and the remaining part at a reduced, coarse-grained, level offer a powerful way to combine the accuracy associated with the atomistic force fields to the sampling speed obtained with coarse-grained (CG) potentials. I

  12. Home Health Aides

    Science.gov (United States)

    ... specifications Help to keep clients engaged in their social networks and communities Home health aides, unlike personal care aides , typically work ... self-care and everyday tasks. They also provide social supports and assistance that enable clients to participate in their ... more information about home health aides, including voluntary credentials for aides, visit ...

  13. Aid and Development

    DEFF Research Database (Denmark)

    Tarp, Finn

    Foreign aid looms large in the public discourse; and international development assistance remains squarely on most policy agendas concerned with growth, poverty and inequality in Africa and elsewhere in the developing world. The present review takes a retrospective look at how foreign aid has...... evolved since World War II in response to a dramatically changing global political and economic context. I review the aid process and associated trends in the volume and distribution of aid and categorize some of the key goals, principles and institutions of the aid system. The evidence on whether aid has...... for aid in the future...

  14. Types of Foreign Aid

    DEFF Research Database (Denmark)

    Bjørnskov, Christian

    Foreign aid is given for many purposes and different intentions, yet most studies treat aid flows as a unitary concept. This paper uses factor analysis to separate aid flows into different types. The main types can be interpreted as aid for economic purposes, social purposes, and reconstruction......; a residual category captures remaining purposes. Estimating the growth effects of separable types of aid suggests that most aid has no effects while reconstruction aid has direct positive effects. Although this type only applies in special circumstances, it has become more prevalent in more recent years....

  15. Laser-fundamentals and applications

    Energy Technology Data Exchange (ETDEWEB)

    Schinagl, W.

    1982-09-01

    The survey article gives an introduction to laser technology. Fundamentals and physical aspects are discussed at large. After a brief historical review and a discussion of the physical fundamentals, important types of laser, characteristics of laser radiation and its applications in medicine are discussed.

  16. The Fundamental Scale of Descriptions

    CERN Document Server

    Febres, Gerardo

    2014-01-01

    The complexity of a system description is a function of the entropy of its symbolic description. Prior to computing the entropy of the system description, an observation scale has to be assumed. In natural language texts, typical scales are binary, characters, and words. However, considering languages as structures built around certain preconceived set of symbols, like words or characters, is only a presumption. This study depicts the notion of the Description Fundamental Scale as a set of symbols which serves to analyze the essence a language structure. The concept of Fundamental Scale is tested using English and MIDI music texts by means of an algorithm developed to search for a set of symbols, which minimizes the system observed entropy, and therefore best expresses the fundamental scale of the language employed. Test results show that it is possible to find the Fundamental Scale of some languages. The concept of Fundamental Scale, and the method for its determination, emerges as an interesting tool to fac...

  17. Understanding materials behavior from atomistic simulations: Case study of al-containing high entropy alloys and thermally grown aluminum oxide

    Science.gov (United States)

    Yinkai Lei

    Atomistic simulation refers to a set of simulation methods that model the materials on the atomistic scale. These simulation methods are faster and cheaper alternative approaches to investigate thermodynamics and kinetics of materials compared to experiments. In this dissertation, atomistic simulation methods have been used to study the thermodynamic and kinetic properties of two material systems, i.e. the entropy of Al-containing high entropy alloys (HEAs) and the vacancy migration energy of thermally grown aluminum oxide. (Abstract shortened by ProQuest.).

  18. [Aged woman's vulnerability related to AIDS].

    Science.gov (United States)

    Silva, Carla Marins; Lopes, Fernanda Maria do Valle Martins; Vargens, Octavio Muniz da Costa

    2010-09-01

    This article is a systhematic literature review including the period from 1994 to 2009, whose objective was to discuss the aged woman's vulnerability in relation to Acquired Imunodeficiency Syndrome (Aids). The search for scientific texts was accomplished in the following databases: Biblioteca Virtual em Saúde, Scientific Eletronic Library Online (SciELO), Literatura Latino-Americana e do Caribe em Ciências da Saúde (LILACS) and Medical Literature Analysis and Retrieval System Online (MEDLINE). The descriptors used were vulnerability, woman and Aids. Eighteen texts were analyzed, including articles in scientific journals, thesis and dissertations. As a conclusion, it was noted that aged women and vulnerability to Aids are directly related, through gender characteristics including submission and that were built historical and socially. We consider as fundamental the development of studies which may generate publications accessible to women, in order to help them see themselves as persons vulnerable to Aids contagion just for being women.

  19. Fundamental principles of heat transfer

    CERN Document Server

    Whitaker, Stephen

    1977-01-01

    Fundamental Principles of Heat Transfer introduces the fundamental concepts of heat transfer: conduction, convection, and radiation. It presents theoretical developments and example and design problems and illustrates the practical applications of fundamental principles. The chapters in this book cover various topics such as one-dimensional and transient heat conduction, energy and turbulent transport, forced convection, thermal radiation, and radiant energy exchange. There are example problems and solutions at the end of every chapter dealing with design problems. This book is a valuable int

  20. Fundamentals of technology project management

    CERN Document Server

    Garton, Colleen

    2012-01-01

    Designed to provide software engineers, students, and IT professionals with an understanding of the fundamentals of project management in the technology/IT field, this book serves as a practical introduction to the subject. Updated with information on how Fundamentals of Project Management integrates with and complements Project Management Institute''s Project Management Body of Knowledge, this collection explains fundamental methodologies and techniques while also discussing new technology, tools, and virtual work environments. Examples and case studies are based on technology projects, and t

  1. Aid and growth regressions

    DEFF Research Database (Denmark)

    Hansen, Henrik; Tarp, Finn

    2001-01-01

    This paper examines the relationship between foreign aid and growth in real GDP per capita as it emerges from simple augmentations of popular cross country growth specifications. It is shown that aid in all likelihood increases the growth rate, and this result is not conditional on ‘good’ policy....... There are, however, decreasing returns to aid, and the estimated effectiveness of aid is highly sensitive to the choice of estimator and the set of control variables. When investment and human capital are controlled for, no positive effect of aid is found. Yet, aid continues to impact on growth via...

  2. Aid and Development

    DEFF Research Database (Denmark)

    Tarp, Finn

    evolved since World War II in response to a dramatically changing global political and economic context. I review the aid process and associated trends in the volume and distribution of aid and categorize some of the key goals, principles and institutions of the aid system. The evidence on whether aid has......Foreign aid looms large in the public discourse; and international development assistance remains squarely on most policy agendas concerned with growth, poverty and inequality in Africa and elsewhere in the developing world. The present review takes a retrospective look at how foreign aid has...

  3. Aid and development

    DEFF Research Database (Denmark)

    Tarp, Finn

    2006-01-01

    evolved since World War II in response to a dramatically changing global political and economic context. I review the aid process and associated trends in the volume and distribution of aid and categorize some of the key goals, principles and institutions of the aid system. The evidence on whether aid has......Foreign aid looms large in the public discourse; and international development assistance remains squarely on most policy agendas concerned with growth, poverty and inequality in Africa and elsewhere in the developing world. The present review takes a retrospective look at how foreign aid has...

  4. Coupling-of-length-scale approach for multiscale atomistic-continuum simulations: Atomistically-induced stress distributions in Si/Si_3N4 nanopixels

    Science.gov (United States)

    Lidorikis, Elefterios; Bachlechner, Martina E.; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya; Voyiadjis, George; Madhukar, Anupam

    2001-03-01

    A hybrid molecular-dynamics and finite-element simulation approach has been used to investigate stress distributions in Si(111) nanopixels covered with both crystalline and amorphous Si_3N4 thin films. Surfaces, lattice-mismatched interfaces, edges, and corners create stress fields on the order of 1 GPa inside the Si substrate with patterns that cannot be reproduced by a continuum approach alone. For these atomistically-induced inhomogeneouse stresses, the hybrid simulation approach provides an excellent agreement with the standard molecular dynamics, with considerably less computational costs.

  5. Coupling Length Scales for Multiscale Atomistics-Continuum Simulations: Atomistically Induced Stress Distributions in Si/Si3N4 Nanopixels

    Science.gov (United States)

    Lidorikis, Elefterios; Bachlechner, Martina E.; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya; Voyiadjis, George Z.

    2001-08-01

    A hybrid molecular-dynamics (MD) and finite-element simulation approach is used to study stress distributions in silicon/silicon-nitride nanopixels. The hybrid approach provides atomistic description near the interface and continuum description deep into the substrate, increasing the accessible length scales and greatly reducing the computational cost. The results of the hybrid simulation are in good agreement with full multimillion-atom MD simulations: atomic structures at the lattice-mismatched interface between amorphous silicon nitride and silicon induce inhomogeneous stress patterns in the substrate that cannot be reproduced by a continuum approach alone.

  6. Atomistic modelling of residual stress at UO2 surfaces.

    Science.gov (United States)

    Arayro, Jack; Tréglia, Guy; Ribeiro, Fabienne

    2016-01-13

    Modelling oxide surface behaviour is of both technological and fundamental interest. In particular, in the case of the UO2 system, which is of major importance in the nuclear industry, it is essential to account for the link between microstructure and macroscopic mechanical properties. Indeed micromechanical models at the mesoscale need to be supplied by the energetic and stress data calculated at the nanoscale. In this framework, we present a theoretical study, coupling an analytical model and thermostatistical simulation to investigate the modifications induced by the presence of a surface regarding atomic relaxation and energetic and stress profiles. In particular, we show that the surface effective thickness as well as the stress profile, which are required by micromechanical approaches, are strongly anisotropic.

  7. Fundamental approach to discrete mathematics

    CERN Document Server

    Acharjya, DP

    2005-01-01

    Salient Features Mathematical logic, fundamental concepts, proofs and mathematical induction (Chapter 1) Set theory, fundamental concepts, theorems, proofs, Venn diagrams, product of sets, application of set theory and fundamental products (Chapter 2) An introduction to binary relations and concepts, graphs, arrow diagrams, relation matrix, composition of relations, types of relation, partial order relations, total order relation, closure of relations, poset, equivalence classes and partitions. (Chapter 3) An introduction to functions and basic concepts, graphs, composition of functions, floor and ceiling function, characteristic function, remainder function, signum function and introduction to hash function. (Chapter 4) The algebraic structure includes group theory and ring theory. Group theory includes group, subgroups, cyclic group, cosets, homomorphism, introduction to codes and group codes and error correction for block code. The ring theory includes general definition, fundamental concepts, integra...

  8. Quantum mechanics I the fundamentals

    CERN Document Server

    Rajasekar, S

    2015-01-01

    Quantum Mechanics I: The Fundamentals provides a graduate-level account of the behavior of matter and energy at the molecular, atomic, nuclear, and sub-nuclear levels. It covers basic concepts, mathematical formalism, and applications to physically important systems.

  9. Expected Devaluation and Economic Fundamentals

    OpenAIRE

    Alun H. Thomas

    1993-01-01

    Recent incidents of exchange rate collapse have provoked interest in the extent to which such events are determined by economic fundamentals. This paper considers whether interest rate differentials are appropriate measures of the risk of devaluation and whether this measure of devaluation risk reflects the movements of variables which capture internal and external balance. The paper finds that interest rate differentials reflect devaluation risk but that movements in fundamental variables ha...

  10. Conjugated polyelectrolytes fundamentals and applications

    CERN Document Server

    Liu, Bin

    2013-01-01

    This is the first monograph to specifically focus on fundamentals and applications of polyelectrolytes, a class of molecules that gained substantial interest due to their unique combination of properties. Combining both features of organic semiconductors and polyelectrolytes, they offer a broad field for fundamental research as well as applications to analytical chemistry, optical imaging, and opto-electronic devices. The initial chapters introduce readers to the synthesis, optical and electrical properties of various conjugated polyelectrolytes. This is followed by chapters on the applica

  11. State Aid as a Defence for Public Authorities?

    DEFF Research Database (Denmark)

    Ølykke, Grith Skovgaard

    2016-01-01

    of consistent interpretation, which it considered could provide various solutions for the national court to draw all the necessary consequences of the possible breach of the duty to notify State aid. In the alternative, the CJEU considered the principle of effectiveness and found that due to the fundamental...... principle of State aid control, the national court’s broad interpretation of the principle of res judicata could not be retained. The judgment cements the specific limitation on national principles of res judicata in a State aid context and tropicalises the issue of how breach of State aid law by public...

  12. HIV/AIDS Coinfection

    Science.gov (United States)

    ... Laotian Mongolian Spanish Turkish Vietnamese Hindi Subscribe HIV/AIDS Coinfection Approximately 10% of the HIV-infected population ... Control and Prevention website to learn about HIV/AIDS and Viral Hepatitis guidelines and resources. Home About ...

  13. HIV/AIDS Basics

    Science.gov (United States)

    ... Partner Spotlight Awareness Days Get Tested Find an HIV testing site near you. Enter ZIP code or ... AIDS Get Email Updates on AAA Anonymous Feedback HIV/AIDS Media Infographics Syndicated Content Podcasts Slide Sets ...

  14. Neurological Complications of AIDS

    Science.gov (United States)

    ... in recent years has improved significantly because of new drugs and treatments. AIDS clinicians often fail to recognize ... in recent years has improved significantly because of new drugs and treatments. AIDS clinicians often fail to recognize ...

  15. Nanoscale finite element models for vibrations of single-walled carbon nanotubes:atomistic versus continuum

    Institute of Scientific and Technical Information of China (English)

    R ANSARI; S ROUHI; M ARYAYI

    2013-01-01

    By the atomistic and continuum finite element models, the free vibration behavior of single-walled carbon nanotubes (SWCNTs) is studied. In the atomistic finite element model, the bonds and atoms are modeled by the beam and point mass elements, respectively. The molecular mechanics is linked to structural mechanics to determine the elastic properties of the mentioned beam elements. In the continuum finite element approach, by neglecting the discrete nature of the atomic structure of the nanotubes, they are modeled with shell elements. By both models, the natural frequencies of SWCNTs are computed, and the effects of the geometrical parameters, the atomic structure, and the boundary conditions are investigated. The accuracy of the utilized methods is verified in comparison with molecular dynamic simulations. The molecular structural model leads to more reliable results, especially for lower aspect ratios. The present analysis provides valuable information about application of continuum models in the investigation of the mechanical behaviors of nanotubes.

  16. Atomistic electrodynamics simulations of bare and ligand-coated nanoparticles in the quantum size regime.

    Science.gov (United States)

    Chen, Xing; Moore, Justin E; Zekarias, Meserret; Jensen, Lasse

    2015-11-10

    The optical properties of metallic nanoparticles with nanometre dimensions exhibit features that cannot be described by classical electrodynamics. In this quantum size regime, the near-field properties are significantly modified and depend strongly on the geometric arrangements. However, simulating realistically sized systems while retaining the atomistic description remains computationally intractable for fully quantum mechanical approaches. Here we introduce an atomistic electrodynamics model where the traditional description of nanoparticles in terms of a macroscopic homogenous dielectric constant is replaced by an atomic representation with dielectric properties that depend on the local chemical environment. This model provides a unified description of bare and ligand-coated nanoparticles, as well as strongly interacting nanoparticle dimer systems. The non-local screening owing to an inhomogeneous ligand layer is shown to drastically modify the near-field properties. This will be important to consider in optimization of plasmonic nanostructures for near-field spectroscopy and sensing applications.

  17. Atomistic simulation of grain boundary structure in a series of B2 intermetallics

    Energy Technology Data Exchange (ETDEWEB)

    Mutasa, B. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Engineering; Farkas, D. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Engineering

    1996-08-01

    Using molecular statics and interatomic potentials of the embedded atom type, the relaxed atomistic grain boundary structures in B2 aluminides were investigated in order to study trends in a series of B2 compounds. The compounds studied: FeAl, NiAl and CoAl show increasing anti-phase boundary energies. The atomistic structure of the {Sigma}=5(310)[100] and {Sigma}=5(210)[100] symmetrical tilt grain boundaries in these compounds was studied considering possible variations of local chemical composition on grain boundary energetics. The structures obtained for the three alloys are very similar. A discussion of the trends in energetics across this series of compounds is entered into. (orig.)

  18. Multiscale Modeling of Carbon/Phenolic Composite Thermal Protection Materials: Atomistic to Effective Properties

    Science.gov (United States)

    Arnold, Steven M.; Murthy, Pappu L.; Bednarcyk, Brett A.; Lawson, John W.; Monk, Joshua D.; Bauschlicher, Charles W., Jr.

    2016-01-01

    Next generation ablative thermal protection systems are expected to consist of 3D woven composite architectures. It is well known that composites can be tailored to achieve desired mechanical and thermal properties in various directions and thus can be made fit-for-purpose if the proper combination of constituent materials and microstructures can be realized. In the present work, the first, multiscale, atomistically-informed, computational analysis of mechanical and thermal properties of a present day - Carbon/Phenolic composite Thermal Protection System (TPS) material is conducted. Model results are compared to measured in-plane and out-of-plane mechanical and thermal properties to validate the computational approach. Results indicate that given sufficient microstructural fidelity, along with lowerscale, constituent properties derived from molecular dynamics simulations, accurate composite level (effective) thermo-elastic properties can be obtained. This suggests that next generation TPS properties can be accurately estimated via atomistically informed multiscale analysis.

  19. Aid and growth regressions

    DEFF Research Database (Denmark)

    Hansen, Henrik; Tarp, Finn

    2001-01-01

    . There are, however, decreasing returns to aid, and the estimated effectiveness of aid is highly sensitive to the choice of estimator and the set of control variables. When investment and human capital are controlled for, no positive effect of aid is found. Yet, aid continues to impact on growth via...... investment. We conclude by stressing the need for more theoretical work before this kind of cross-country regressions are used for policy purposes....

  20. Designing State Aid Formulas

    Science.gov (United States)

    Zhao, Bo; Bradbury, Katharine

    2009-01-01

    This paper designs a new equalization-aid formula based on fiscal gaps of local communities. When states are in transition to a new local aid formula, the issue of whether and how to hold existing aid harmless poses a challenge. The authors show that some previous studies and the formulas derived from them give differential weights to existing and…

  1. Determinants of State Aid

    NARCIS (Netherlands)

    Buiren, K.; Brouwer, E.

    2010-01-01

    From economic theory we derive a set of hypotheses on the determination of state aid. Econometric analysis on EU state aid panel data is carried out to test whether the determinants we expect on the basis of theory, correspond to the occurrence of state aid in practice in the EU. We find that politi

  2. Fever: First Aid

    Science.gov (United States)

    First aid Fever: First aid Fever: First aid By Mayo Clinic Staff A fever is a rise in body temperature. It's usually a sign of infection. The ... 2 C) or higher Should I treat a fever? When you or your child is sick, the ...

  3. Stroke: First Aid

    Science.gov (United States)

    First aid Stroke: First aid Stroke: First aid By Mayo Clinic Staff A stroke occurs when there's bleeding into your brain or when normal blood flow to ... next several hours. Seek immediate medical assistance. A stroke is a true emergency. The sooner treatment is ...

  4. Aid and Development

    DEFF Research Database (Denmark)

    Tarp, Finn; Arndt, Channing; Jones, Edward Samuel

    inputs. We take as our point of departure a growth accounting analysis and review both intended and unintended effects of aid. Mozambique has benefited from sustained aid inflows in conflict, post-conflict and reconstruction periods. In each of these phases aid has made an unambiguous, positive...

  5. Atomistic-continuum modeling of ultrafast laser-induced melting of silicon targets

    OpenAIRE

    Lipp, Vladimir

    2015-01-01

    In this work, we present an atomistic-continuum model for simulations of ultrafast laser-induced melting processes in semiconductors on the example of silicon. The kinetics of transient non-equilibrium phase transition mechanisms is addressed with MD method on the atomic level, whereas the laser light absorption, strong generated electron-phonon nonequilibrium, fast heat conduction, and photo-excited free carrier diffusion are accounted for with a continuum TTM-like model (called nTTM). First...

  6. Atomistic Failure Mechanism of Single Wall Carbon Nanotubes with Small Diameters

    Institute of Scientific and Technical Information of China (English)

    JI Dong; GAO Xiang; KONG Xiang-Yang; LI Jia-Ming

    2007-01-01

    @@ Single wall carbon nanotubes with small diameters (< 5.0 (A)) subjected to bending deformation are simulated by orthogonal tight-binding molecular dynamics approach. Based on the calculations of C-C bond stretching and breaking in the bending nanotubes, we elucidate the atomistic failure mechanisms of nanotube with small diameters. In the folding zone of bending nanotube, a large elongation of C-C bonds occurs, accounting for the superelastic behaviour.

  7. Idealized vs. Realistic Microstructures: An Atomistic Simulation Case Study on γ/γ′ Microstructures

    Directory of Open Access Journals (Sweden)

    Aruna Prakash

    2017-01-01

    Full Text Available Single-crystal Ni-base superalloys, consisting of a two-phase γ/ γ ′ microstructure, retain high strengths at elevated temperatures and are key materials for high temperature applications, like, e.g., turbine blades of aircraft engines. The lattice misfit between the γ and γ ′ phases results in internal stresses, which significantly influence the deformation and creep behavior of the material. Large-scale atomistic simulations that are often used to enhance our understanding of the deformation mechanisms in such materials must accurately account for such misfit stresses. In this work, we compare the internal stresses in both idealized and experimentally-informed, i.e., more realistic, γ/ γ ′ microstructures. The idealized samples are generated by assuming, as is frequently done, a periodic arrangement of cube-shaped γ ′ particles with planar γ/ γ ′ interfaces. The experimentally-informed samples are generated from two different sources to produce three different samples—the scanning electron microscopy micrograph-informed quasi-2D atomistic sample and atom probe tomography-informed stoichiometric and non-stoichiometric atomistic samples. Additionally, we compare the stress state of an idealized embedded cube microstructure with finite element simulations incorporating 3D periodic boundary conditions. Subsequently, we study the influence of the resulting stress state on the evolution of dislocation loops in the different samples. The results show that the stresses in the atomistic and finite element simulations are almost identical. Furthermore, quasi-2D boundary conditions lead to a significantly different stress state and, consequently, different evolution of the dislocation loop, when compared to samples with fully 3D boundary conditions.

  8. Atomistic resolution structure and dynamics of lipid bilayers in simulations and experiments.

    Science.gov (United States)

    Ollila, O H Samuli; Pabst, Georg

    2016-10-01

    Accurate details on the sampled atomistic resolution structures of lipid bilayers can be experimentally obtained by measuring C-H bond order parameters, spin relaxation rates and scattering form factors. These parameters can be also directly calculated from the classical atomistic resolution molecular dynamics simulations (MD) and compared to the experimentally achieved results. This comparison measures the simulation model quality with respect to 'reality'. If agreement is sufficient, the simulation model gives an atomistic structural interpretation of the acquired experimental data. Significant advance of MD models is made by jointly interpreting different experiments using the same structural model. Here we focus on phosphatidylcholine lipid bilayers, which out of all model membranes have been studied mostly by experiments and simulations, leading to the largest available dataset. From the applied comparisons we conclude that the acyl chain region structure and rotational dynamics are generally well described in simulation models. Also changes with temperature, dehydration and cholesterol concentration are qualitatively correctly reproduced. However, the quality of the underlying atomistic resolution structural changes is uncertain. Even worse, when focusing on the lipid bilayer properties at the interfacial region, e.g. glycerol backbone and choline structures, and cation binding, many simulation models produce an inaccurate description of experimental data. Thus extreme care must be applied when simulations are applied to understand phenomena where the interfacial region plays a significant role. This work is done by the NMRlipids Open Collaboration project running at https://nmrlipids.blogspot.fi and https://github.com/NMRLipids. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg.

  9. Atomistic insight into the minimum wear depth of Cu(111) surface

    OpenAIRE

    2013-01-01

    In the present work, we investigate the minimum wear depth of single crystalline Cu(111) under single asperity friction by means of molecular dynamics simulations. The atomistic mechanisms governing the incipient plasticity are elucidated by characterizing specific defect structures and are correlated to the observed mechanical and frictional responses of the material. Furthermore, the effect of probe radius on the friction process is studied. Our simulations indicate that the formation of we...

  10. Welding. FOS: Fundamentals of Service.

    Science.gov (United States)

    John Deere Co., Moline, IL.

    This manual on modern gas and arc welding is one of a series of power mechanics texts and visual aids on the servicing of automotive and off-the-road agricultural and construction equipment. Materials provide basic information with illustrations for use by vocational students and teachers as well as shop servicemen and laymen. The eight sections…

  11. Hydraulics. FOS: Fundamentals of Service.

    Science.gov (United States)

    John Deere Co., Moline, IL.

    This manual on hydraulics is one of a series of power mechanics texts and visual aids for training in the servicing of agricultural and industrial machinery. Focus is on oil hydraulics. Materials provide basic information and illustrations for use by vocational students and teachers as well as shop servicemen and laymen. The twelve chapters focus…

  12. Fasteners. FOS: Fundamentals of Service.

    Science.gov (United States)

    John Deere Co., Moline, IL.

    This manual on fasteners (devices used in home and shop to hold things together) is one of a series of power mechanics texts and visual aids on operation, diagnosis, and repair. Materials provide basic information and illustrations for use by vocational students and teachers as well as shop servicemen and laymen. Seven chapters are included: (1)…

  13. Engines. FOS: Fundamentals of Service.

    Science.gov (United States)

    John Deere Co., Moline, IL.

    This manual on engines is one of a series of power mechanics texts and visual aids for training in servicing of farm and industrial machinery. (Automotive, truck, and bus applications are often covered as well.) Materials provide basic information and illustrations for use by vocational students and teachers as well as shop servicemen and laymen.…

  14. Phase field crystal modelling of the order-to-disordered atomistic structure transition of metallic glasses

    Science.gov (United States)

    Zhang, W.; Mi, J.

    2016-03-01

    Bulk metallic glass composites are a new class of metallic alloy systems that have very high tensile strength, ductility and fracture toughness. This unique combination of mechanical properties is largely determined by the presence of crystalline phases uniformly distributed within the glassy matrix. However, there have been very limited reports on how the crystalline phases are nucleated in the super-cooled liquid and their growth dynamics, especially lack of information on the order-to-disordered atomistic structure transition across the crystalline-amorphous interface. In this paper, we use phase field crystal (PFC) method to study the nucleation and growth of the crystalline phases and the glass formation of the super cooled liquid of a binary alloy. The study is focused on understanding the order-to-disordered transition of atomistic configuration across the interface between the crystalline phases and amorphous matrix of different chemical compositions at different thermal conditions. The capability of using PFC to simulate the order-to-disorder atomistic transition in the bulk material or across the interface is discussed in details.

  15. Markov-chain model of classified atomistic transition states for discrete kinetic Monte Carlo simulations.

    Science.gov (United States)

    Numazawa, Satoshi; Smith, Roger

    2011-10-01

    Classical harmonic transition state theory is considered and applied in discrete lattice cells with hierarchical transition levels. The scheme is then used to determine transitions that can be applied in a lattice-based kinetic Monte Carlo (KMC) atomistic simulation model. The model results in an effective reduction of KMC simulation steps by utilizing a classification scheme of transition levels for thermally activated atomistic diffusion processes. Thermally activated atomistic movements are considered as local transition events constrained in potential energy wells over certain local time periods. These processes are represented by Markov chains of multidimensional Boolean valued functions in three-dimensional lattice space. The events inhibited by the barriers under a certain level are regarded as thermal fluctuations of the canonical ensemble and accepted freely. Consequently, the fluctuating system evolution process is implemented as a Markov chain of equivalence class objects. It is shown that the process can be characterized by the acceptance of metastable local transitions. The method is applied to a problem of Au and Ag cluster growth on a rippled surface. The simulation predicts the existence of a morphology-dependent transition time limit from a local metastable to stable state for subsequent cluster growth by accretion. Excellent agreement with observed experimental results is obtained.

  16. State Representation Approach for Atomistic Time-Dependent Transport Calculations in Molecular Junctions.

    Science.gov (United States)

    Zelovich, Tamar; Kronik, Leeor; Hod, Oded

    2014-08-12

    We propose a new method for simulating electron dynamics in open quantum systems out of equilibrium, using a finite atomistic model. The proposed method is motivated by the intuitive and practical nature of the driven Liouville-von-Neumann equation approach of Sánchez et al. [J. Chem. Phys. 2006, 124, 214708] and Subotnik et al. [J. Chem. Phys. 2009, 130, 144105]. A key ingredient of our approach is a transformation of the Hamiltonian matrix from an atomistic to a state representation of the molecular junction. This allows us to uniquely define the bias voltage across the system while maintaining a proper thermal electronic distribution within the finite lead models. Furthermore, it allows us to investigate complex molecular junctions, including multilead configurations. A heuristic derivation of our working equation leads to explicit expressions for the damping and driving terms, which serve as appropriate electron sources and sinks that effectively "open" the finite model system. Although the method does not forbid it, in practice we find neither violation of Pauli's exclusion principles nor deviation from density matrix positivity throughout our numerical simulations of various tight-binding model systems. We believe that the new approach offers a practical and physically sound route for performing atomistic time-dependent transport calculations in realistic molecular junction models.

  17. A study of conditions for dislocation nucleation in coarser-than-atomistic scale models

    Science.gov (United States)

    Garg, Akanksha; Acharya, Amit; Maloney, Craig E.

    2015-02-01

    We perform atomistic simulations of dislocation nucleation in defect free crystals in 2 and 3 dimensions during indentation with circular (2D) or spherical (3D) indenters. The kinematic structure of the theory of Field Dislocation Mechanics (FDM) is shown to allow the identification of a local feature of the atomistic velocity field in these simulations as indicative of dislocation nucleation. It predicts the precise location of the incipient spatially distributed dislocation field, as shown for the cases of the Embedded Atom Method potential for Al and the Lennard-Jones pair potential. We demonstrate the accuracy of this analysis for two crystallographic orientations in 2D and one in 3D. Apart from the accuracy in predicting the location of dislocation nucleation, the FDM based analysis also demonstrates superior performance than existing nucleation criteria in not persisting in time beyond the nucleation event, as well as differentiating between phase boundary/shear band and dislocation nucleation. Our analysis is meant to facilitate the modeling of dislocation nucleation in coarser-than-atomistic scale models of the mechanics of materials.

  18. The injection of a screw dislocation into a crystal: Atomistics vs. continuum elastodynamics

    Science.gov (United States)

    Verschueren, J.; Gurrutxaga-Lerma, B.; Balint, D. S.; Dini, D.; Sutton, A. P.

    2017-01-01

    The injection (creation) process of a straight screw dislocation is compared atomistically with elastodynamic continuum theory. A method for injecting quiescent screw dislocations into a crystal of tungsten is simulated using non-equilibrium molecular dynamics. The resulting stress fields are compared to the those of elastodynamic solutions for the injection of a quiescent screw dislocation. A number of differences are found: a plane wave emission is observed to emanate from the whole surface of the cut used to create the dislocation, affecting the displacement field along the dislocation line (z), and introducing displacement field components perpendicular to the line (along x and y). It is argued that, in part, this emission is the result of the finite time required to inject the dislocation, whereby the atoms in the cut surface must temporarily be displaced to unstable positions in order to produce the required slip. By modelling this process in the continuum it is shown that the displacements components normal to the dislocation line arise from transient displacements of atoms in the cut surface parallel to x and y. It is shown that once these displacements are included in the elastodynamic continuum formulation the plane wave emission in uz is correctly captured. A detailed comparison between the atomistic and continuum models is then offered, showing that the main atomistic features can also be captured in the continuum.

  19. The Soft Mode Driven Dynamics in Ferroelectric Perovskites at the Nanoscale: An Atomistic Study

    Science.gov (United States)

    McCash, Kevin

    The discovery of ferroelectricity at the nanoscale has incited a lot of interest in perovskite ferroelectrics not only for their potential in device application but also for their potential to expand fundamental understanding of complex phenomena at very small size scales. Unfortunately, not much is known about the dynamics of ferroelectrics at this scale. Many of the widely held theories for ferroelectric materials are based on bulk dynamics which break down when applied to smaller scales. In an effort to increase understanding of nanoscale ferroelectric materials we use atomistic resolution computational simulations to investigate the dynamics of polar perovskites. Within the framework of a well validated effective Hamiltonian model we are able to accurately predict many of the properties of ferroelectric materials at the nanoscale including the response of the soft mode to mechanical boundary conditions and the polarization reversal dynamics of ferroelectric nanowires. Given that the focus of our study is the dynamics of ferroelectric perovskites we begin by developing an effective Hamiltonian based model that could simultaneously describe both static and dynamic properties of such materials. Our study reveals that for ferroelectric perovskites that undergo a sequence of phase transitions, such as BaTiO3. for example, the minimal parameter effective Hamiltonian model is unable to reproduce both static and dynamical properties simultaneously. Nevertheless we developed two sets of parameters that accurately describes the static properties and dynamic properties of BaTiO3 independently. By creating a tool that accurately models the dynamical properties of perovskite ferroelectrics we are able to investigate the frequencies of the soft modes in the perovskite crystal. The lowest energy transverse optical soft modes in perovskite ferroelectrics are known to be cause of the ferroelectric phase transition in these materials and affect a number of electrical properties

  20. Fundamental physics in particle traps

    CERN Document Server

    Vogel, Manuel

    2014-01-01

    This volume provides detailed insight into the field of precision spectroscopy and fundamental physics with particles confined in traps. It comprises experiments with electrons and positrons, protons and antiprotons, antimatter and highly charged ions, together with corresponding theoretical background. Such investigations represent stringent tests of quantum electrodynamics and the Standard model, antiparticle and antimatter research, test of fundamental symmetries, constants, and their possible variations with time and space. They are key to various aspects within metrology such as mass measurements and time standards, as well as promising to further developments in quantum information processing. The reader obtains a valuable source of information suited for beginners and experts with an interest in fundamental studies using particle traps.

  1. Fundamental units: physics and metrology

    CERN Document Server

    Okun, Lev Borisovich

    2003-01-01

    The problem of fundamental units is discussed in the context of achievements of both theoretical physics and modern metrology. On one hand, due to fascinating accuracy of atomic clocks, the traditional macroscopic standards of metrology (second, metre, kilogram) are giving way to standards based on fundamental units of nature: velocity of light $c$ and quantum of action $h$. On the other hand, the poor precision of gravitational constant $G$, which is widely believed to define the ``cube of theories'' and the units of the future ``theory of everything'', does not allow to use $G$ as a fundamental dimensional constant in metrology. The electromagnetic units in SI are actually based on concepts of prerelativistic classical electrodynamics such as ether, electric permitivity and magnetic permeability of vacuum. Concluding remarks are devoted to terminological confusion which accompanies the progress in basic physics and metrology.

  2. Conditional Aid Effectiveness

    DEFF Research Database (Denmark)

    Doucouliagos, Hristos; Paldam, Martin

    The AEL (aid effectiveness literature) studies the effect of development aid using econometrics on macro data. It contains about 100 papers of which a third analyzes conditional models where aid effectiveness depends upon z, so that aid only works for a certain range of the variable. The key term...... in this family of AEL models is thus an interaction term of z times aid. The leading candidates for z are a good policy index and aid itself. In this paper, meta-analysis techniques are used (i) to determine whether the AEL has established the said interaction terms, and (ii) to identify some of the determinants...... of the differences in results between studies. Taking all available studies in consideration, we find no support for conditionality with respect to policy, while conditionality regarding aid itself is dubious. However, the results differ depending on the authors’ institutional affiliation....

  3. Aid and Development

    DEFF Research Database (Denmark)

    Tarp, Finn; Arndt, Channing; Jones, Edward Samuel

    This paper considers the relationship between external aid and development in Mozambique from 1980 to 2004. The main objective is to identify the specific mechanisms through which aid has influenced the developmental trajectory of the country and whether one can plausibly link outcomes to aid...... inputs. We take as our point of departure a growth accounting analysis and review both intended and unintended effects of aid. Mozambique has benefited from sustained aid inflows in conflict, post-conflict and reconstruction periods. In each of these phases aid has made an unambiguous, positive...... contribution both enabling and supporting rapid growth since 1992. At the same time, the proliferation of donors and aid-supported interventions has burdened local administration and there is a distinct need to develop government accountability to its own citizens rather than donor agencies. In ensuring...

  4. China vs. AIDS

    Institute of Scientific and Technical Information of China (English)

    LURUCAI

    2004-01-01

    CHINA's first HIV positive diagnosis was in 1985, the victim an ArgentineAmerican. At that time most Chinese,medical workers included, thought of AIDS as a phenomenon occurring outside of China. Twenty years later, the number of HIV/AIDS patients has risen alarmingly. In 2003, the Chinese Ministry of Health launched an AIDS Epidemiological Investigation across China with the support of the WHO and UN AIDS Program. Its results show that there are currently 840,000 HIV carriers, including 80,000 people with full-blown AIDS, in 31 Chinese provinces, municipalities and autonomous regions. This means China has the second highest number of HIV/AIDS cases in Asia and 14th highest in the world. Statistics from the Chinese Venereal Disease and AIDS Prevention Association indicate that the majority of Chinese HIV carriers are young to middle aged, more than half of them between the ages of 20 and 29.

  5. Aid Effectiveness on Growth

    DEFF Research Database (Denmark)

    Doucouliagos, Hristos; Paldam, Martin

    The AEL (aid effectiveness literature) is econo¬metric studies of the macroeconomic effects of development aid. It contains about 100 papers of which 68 are reduced form estimates of theeffect of aid on growth in the recipient country. The raw data show that growth is unconnected to aid......, but the AEL has put so much structure on the data that all results possible have emerged. The present meta study considers both the best-set of the 68 papers and the all-set of 543 regressions published. Both sets have a positive average aid-growth elasticity, but it is small and insignificant: The AEL has...... betweenstudies is real. In particular, the aid-growth association is stronger for Asian countries, and the aid-growth association is shown to have been weaker in the 1970s....

  6. RFID design fundamentals and applications

    CERN Document Server

    Lozano-Nieto, Albert

    2010-01-01

    RFID is an increasingly pervasive tool that is now used in a wide range of fields. It is employed to substantiate adherence to food preservation and safety standards, combat the circulation of counterfeit pharmaceuticals, and verify authenticity and history of critical parts used in aircraft and other machinery-and these are just a few of its uses. Goes beyond deployment, focusing on exactly how RFID actually worksRFID Design Fundamentals and Applications systematically explores the fundamental principles involved in the design and characterization of RFID technologies. The RFID market is expl

  7. Fundamental approach to discrete mathematics

    CERN Document Server

    Acharjya, DP

    2009-01-01

    About the Book: The book `Fundamental Approach to Discrete Mathematics` is a required part of pursuing a computer science degree at most universities. It provides in-depth knowledge to the subject for beginners and stimulates further interest in the topic. The salient features of this book include: Strong coverage of key topics involving recurrence relation, combinatorics, Boolean algebra, graph theory and fuzzy set theory. Algorithms and examples integrated throughout the book to bring clarity to the fundamental concepts. Each concept and definition is followed by thoughtful examples.

  8. Fundamental Research and Developing Countries

    CERN Document Server

    Narison, Stéphan

    2002-01-01

    In the first part of this report, I discuss the sociological role of fundamental research in Developing Countries (DC) and how to realize this program. In the second part, I give a brief and elementary introduction to the field of high-energy physics (HEP), accessible to a large audience not necessary physicists. The aim of this report is to make politicians and financial backers aware on the long-term usefulness of fundamental research in DC and on the possible globalisation of HEP and, in general, of science.

  9. Astrophysical probes of fundamental physics

    Energy Technology Data Exchange (ETDEWEB)

    Martins, C.J.A.P. [Centro de Astrofisica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); DAMTP, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

    2009-10-15

    I review the motivation for varying fundamental couplings and discuss how these measurements can be used to constrain fundamental physics scenarios that would otherwise be inaccessible to experiment. I highlight the current controversial evidence for varying couplings and present some new results. Finally I focus on the relation between varying couplings and dark energy, and explain how varying coupling measurements might be used to probe the nature of dark energy, with some advantages over standard methods. In particular I discuss what can be achieved with future spectrographs such as ESPRESSO and CODEX.

  10. The fundamentals of mathematical analysis

    CERN Document Server

    Fikhtengol'ts, G M

    1965-01-01

    The Fundamentals of Mathematical Analysis, Volume 1 is a textbook that provides a systematic and rigorous treatment of the fundamentals of mathematical analysis. Emphasis is placed on the concept of limit which plays a principal role in mathematical analysis. Examples of the application of mathematical analysis to geometry, mechanics, physics, and engineering are given. This volume is comprised of 14 chapters and begins with a discussion on real numbers, their properties and applications, and arithmetical operations over real numbers. The reader is then introduced to the concept of function, i

  11. Fundamental Composite (Goldstone) Higgs Dynamics

    DEFF Research Database (Denmark)

    Cacciapaglia, G.; Sannino, Francesco

    2014-01-01

    We provide a unified description, both at the effective and fundamental Lagrangian level, of models of composite Higgs dynamics where the Higgs itself can emerge, depending on the way the electroweak symmetry is embedded, either as a pseudo-Goldstone boson or as a massive excitation...... transforming according to the fundamental representation of the gauge group. This minimal choice enables us to use recent first principle lattice results to make the first predictions for the massive spectrum for models of composite (Goldstone) Higgs dynamics. These results are of the upmost relevance to guide...

  12. Ion beam processing of surfaces and interfaces. Modeling and atomistic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Liedke, Bartosz

    2011-03-24

    Self-organization of regular surface pattern under ion beam erosion was described in detail by Navez in 1962. Several years later in 1986 Bradley and Harper (BH) published the first self-consistent theory on this phenomenon based on the competition of surface roughening described by Sigmund's sputter theory and surface smoothing by Mullins-Herring diffusion. Many papers that followed BH theory introduced other processes responsible for the surface patterning e.g. viscous flow, redeposition, phase separation, preferential sputtering, etc. The present understanding is still not sufficient to specify the dominant driving forces responsible for self-organization. 3D atomistic simulations can improve the understanding by reproducing the pattern formation with the detailed microscopic description of the driving forces. 2D simulations published so far can contribute to this understanding only partially. A novel program package for 3D atomistic simulations called TRIDER (TRansport of Ions in matter with DEfect Relaxation), which unifies full collision cascade simulation with atomistic relaxation processes, has been developed. The collision cascades are provided by simulations based on the Binary Collision Approximation, and the relaxation processes are simulated with the 3D lattice kinetic Monte-Carlo method. This allows, without any phenomenological model, a full 3D atomistic description on experimental spatiotemporal scales. Recently discussed new mechanisms of surface patterning like ballistic mass drift or the dependence of the local morphology on sputtering yield are inherently included in our atomistic approach. The atomistic 3D simulations do not depend so much on experimental assumptions like reported 2D simulations or continuum theories. The 3D computer experiments can even be considered as 'cleanest' possible experiments for checking continuum theories. This work aims mainly at the methodology of a novel atomistic approach, showing that: (i) In

  13. Composing Europe's Fundamental Rights Area

    DEFF Research Database (Denmark)

    Storgaard, Louise Halleskov

    2015-01-01

    The article offers a perspective on how the objective of a strong and coherent European protection standard pursued by the fundamental rights amendments of the Lisbon Treaty can be achieved, as it proposes a discursive pluralistic framework to understand and guide the relationship between the EU ...

  14. Status of Fundamental Physics Program

    Science.gov (United States)

    Lee, Mark C.

    2003-01-01

    Update of the Fundamental Physics Program. JEM/EF Slip. 2 years delay. Reduced budget. Community support and advocacy led by Professor Nick Bigelow. Reprogramming led by Fred O Callaghan/JPL team. LTMPF M1 mission (DYNAMX and SUMO). PARCS. Carrier re baselined on JEM/EF.

  15. Different Variants of Fundamental Portfolio

    Directory of Open Access Journals (Sweden)

    Tarczyński Waldemar

    2014-06-01

    Full Text Available The paper proposes the fundamental portfolio of securities. This portfolio is an alternative for the classic Markowitz model, which combines fundamental analysis with portfolio analysis. The method’s main idea is based on the use of the TMAI1 synthetic measure and, in limiting conditions, the use of risk and the portfolio’s rate of return in the objective function. Different variants of fundamental portfolio have been considered under an empirical study. The effectiveness of the proposed solutions has been related to the classic portfolio constructed with the help of the Markowitz model and the WIG20 market index’s rate of return. All portfolios were constructed with data on rates of return for 2005. Their effectiveness in 2006- 2013 was then evaluated. The studied period comprises the end of the bull market, the 2007-2009 crisis, the 2010 bull market and the 2011 crisis. This allows for the evaluation of the solutions’ flexibility in various extreme situations. For the construction of the fundamental portfolio’s objective function and the TMAI, the study made use of financial and economic data on selected indicators retrieved from Notoria Serwis for 2005.

  16. Biological Computing Fundamentals and Futures

    OpenAIRE

    Akula, Balaji; Cusick, James

    2009-01-01

    The fields of computing and biology have begun to cross paths in new ways. In this paper a review of the current research in biological computing is presented. Fundamental concepts are introduced and these foundational elements are explored to discuss the possibilities of a new computing paradigm. We assume the reader to possess a basic knowledge of Biology and Computer Science

  17. Fundamentals of EU VAT law

    NARCIS (Netherlands)

    van Doesum, A.; van Kesteren, H.W.M.; van Norden, G.J.

    2016-01-01

    Fundamentals of EU VAT Law aims at providing a deep insight into the systematics, the functioning and the principles of the European Value Added Tax (VAT) system. VAT is responsible for generating approximately EUR 903 billion per year in tax revenues across the European Union – revenues that play a

  18. Brake Fundamentals. Automotive Articulation Project.

    Science.gov (United States)

    Cunningham, Larry; And Others

    Designed for secondary and postsecondary auto mechanics programs, this curriculum guide contains learning exercises in seven areas: (1) brake fundamentals; (2) brake lines, fluid, and hoses; (3) drum brakes; (4) disc brake system and service; (5) master cylinder, power boost, and control valves; (6) parking brakes; and (7) trouble shooting. Each…

  19. Fundamental stellar properties from asteroseismology

    DEFF Research Database (Denmark)

    Silva Aguirre, V.; Casagrande, L.; Miglio, A.

    2013-01-01

    Accurate characterization of stellar populations is of prime importance to correctly understand the formation and evolution process of our Galaxy. The field of asteroseismology has been particularly successful in such an endeavor providing fundamental parameters for large samples of stars in diff...

  20. Calorimetry fundamentals, instrumentation and applications

    CERN Document Server

    Sarge, Stefan M; Hemminger, Wolfgang

    2014-01-01

    Clearly divided into three parts, this practical book begins by dealing with all fundamental aspects of calorimetry. The second part looks at the equipment used and new developments. The third and final section provides measurement guidelines in order to obtain the best results. The result is optimized knowledge for users of this technique, supplemented with practical tips and tricks.

  1. Fundamentals of Microelectronics Processing (VLSI).

    Science.gov (United States)

    Takoudis, Christos G.

    1987-01-01

    Describes a 15-week course in the fundamentals of microelectronics processing in chemical engineering, which emphasizes the use of very large scale integration (VLSI). Provides a listing of the topics covered in the course outline, along with a sample of some of the final projects done by students. (TW)

  2. Fundamentals of Welding. Teacher Edition.

    Science.gov (United States)

    Fortney, Clarence; And Others

    These instructional materials assist teachers in improving instruction on the fundamentals of welding. The following introductory information is included: use of this publication; competency profile; instructional/task analysis; related academic and workplace skills list; tools, materials, and equipment list; and 27 references. Seven units of…

  3. Fundamentals: IVC and computer science

    NARCIS (Netherlands)

    Gozalvez, Javier; Haerri, Jerome; Hartenstein, Hannes; Heijenk, Geert; Kargl, Frank; Petit, Jonathan; Scheuermann, Björn; Tieler, Tessa; Altintas, O.; Dressler, F.; Hartenstein, H.; Tonguz, O.K.

    2013-01-01

    The working group on “Fundamentals: IVC and Computer Science” discussed the lasting value of achieved research results as well as potential future directions in the field of inter- vehicular communication. Two major themes ‘with variations’ were the dependence on a specific technology (particularly

  4. Aid and Growth

    DEFF Research Database (Denmark)

    Arndt, Channing; Jones, Edward Samuel; Tarp, Finn

    The micro-macro paradox has been revived. Despite broadly positive evaluations at the micro and meso-levels, recent literature has turned decidedly pessimistic with respect to the ability of foreign aid to foster economic growth. Policy implications, such as the complete cessation of aid to Africa......, are being drawn on the basis of fragile evidence. This paper first assesses the aid-growth literature with a focus on recent contributions. The aid-growth literature is then framed, for the first time, in terms of the Rubin Causal Model, applied at the macroeconomic level. Our results show that aid has...... a positive and statistically significant causal effect on growth over the long run with point estimates at levels suggested by growth theory. We conclude that aid remains an important tool for enhancing the development prospects of poor nations....

  5. Aid and Growth

    DEFF Research Database (Denmark)

    Arndt, Channing; Jones, Edward Samuel; Tarp, Finn

    2009-01-01

    The micro-macro paradox has been revived. Despite broadly positive evaluations at the micro and meso-levels, recent literature has turned decidedly pessimistic with respect to the ability of foreign aid to foster economic growth. Policy implications, such as the complete cessation of aid to Africa......, are being drawn on the basis of fragile evidence. This paper first assesses the aid-growth literature with a focus on recent contributions. The aid-growth literature is then framed, for the first time, in terms of the Rubin Causal Model, applied at the macroeconomic level. Our results show that aid has...... a positive and statistically significant causal effect on growth over the long run with point estimates at levels suggested by growth theory. We conclude that aid remains an important tool for enhancing the development prospects of poor nations....

  6. AIDS in South Africa.

    Science.gov (United States)

    Ijsselmuiden, C; Evian, C; Matjilla, J; Steinberg, M; Schneider, H

    1993-01-01

    The National AIDS Convention in South Africa (NACOSA) in October 1992 was the first real attempt to address HIV/AIDS. In Soweto, government, the African National Congress, nongovernmental organizations, and organized industry and labor representatives worked for 2 days to develop a national plan of action, but it did not result in a united effort to fight AIDS. The highest HIV infection rates in South Africa are among the KwaZulu in Natal, yet the Inkatha Freedom Party did not attend NACOSA. This episode exemplifies the key obstacles for South Africa to prevent and control AIDS. Inequality of access to health care may explain why health workers did not diagnose the first AIDS case in blacks until 1985. Migrant labor, Bantu education, and uprooted communities affect the epidemiology of HIV infection. Further, political and social polarization between blacks and whites contributes to a mindset that AIDS is limited to the other race which only diminishes the personal and collective sense of susceptibility and the volition and aptitude to act. The Department of National Health and Population Development's voluntary register of anonymously reported cases of AIDS specifies 1517 cumulative AIDS cases (October 1992), but this number is low. Seroprevalence studies show between 400,000-450,000 HIV positive cases. Public hospitals cannot give AIDS patients AZT and DDI. Few communities provided community-based care. Not all hospitals honor confidentiality and patients' need for autonomy. Even though HIV testing is not mandatory, it is required sometimes, e.g., HIV testing of immigrants. AIDS Training, Information and Counselling Centers are in urban areas, but not in poor areas where the need is most acute. The government just recently developed in AIDS education package for schools, but too many people consider it improper, so it is not being used. The poor quality education provided blacks would make it useless anyhow. Lifting of the academic boycott will allow South African

  7. JPRS Report, Epidemiology, Aids

    Science.gov (United States)

    2007-11-02

    at home. For this they can thank the National Federation of Gays and Lesbians (LBL). -To develop an adequate core of specialists in AIDS prevention... Homosexuality [Vusie Ginindza; Mbabane THE TIMES OF SWAZILAND, 15 May 91] ...................................... 4 JPRS-TEP-91-012 5 June 1991 2 AIDS TANZANIA...sensitivity and not to sensa- tionalize the issue. Health Workers ’Alarmed’ at rise in AIDS, Homosexuality SWAZILAND MB1505085891 Mbabane THE TIMES

  8. Radiographic imaging of aids

    CERN Document Server

    Mahmoud, M B

    2002-01-01

    The acquired immunodeficiency syndrome (AIDS) has impacted the civilized world like no other disease. This research aimed to discuss some of the main aids-related complications and their detection by radiology tests, specifically central nervous system and musculoskeletal system disorders. The objectives are: to show specific characteristics of various diseases of HIV patient, to analyze the effect of pathology in patients by radiology, to enhance the knowledge of technologists in aids imaging and to improve communication skills between patient and radiology technologists.

  9. Music and hearing aids.

    Science.gov (United States)

    Madsen, Sara M K; Moore, Brian C J

    2014-10-31

    The signal processing and fitting methods used for hearing aids have mainly been designed to optimize the intelligibility of speech. Little attention has been paid to the effectiveness of hearing aids for listening to music. Perhaps as a consequence, many hearing-aid users complain that they are not satisfied with their hearing aids when listening to music. This issue inspired the Internet-based survey presented here. The survey was designed to identify the nature and prevalence of problems associated with listening to live and reproduced music with hearing aids. Responses from 523 hearing-aid users to 21 multiple-choice questions are presented and analyzed, and the relationships between responses to questions regarding music and questions concerned with information about the respondents, their hearing aids, and their hearing loss are described. Large proportions of the respondents reported that they found their hearing aids to be helpful for listening to both live and reproduced music, although less so for the former. The survey also identified problems such as distortion, acoustic feedback, insufficient or excessive gain, unbalanced frequency response, and reduced tone quality. The results indicate that the enjoyment of listening to music with hearing aids could be improved by an increase of the input and output dynamic range, extension of the low-frequency response, and improvement of feedback cancellation and automatic gain control systems.

  10. Fundamentals of estuarine physical oceanography

    CERN Document Server

    Bruner de Miranda, Luiz; Kjerfve, Björn; Castro Filho, Belmiro Mendes de

    2017-01-01

    This book provides an introduction to the complex system functions, variability and human interference in ecosystem between the continent and the ocean. It focuses on circulation, transport and mixing of estuarine and coastal water masses, which is ultimately related to an understanding of the hydrographic and hydrodynamic characteristics (salinity, temperature, density and circulation), mixing processes (advection and diffusion), transport timescales such as the residence time and the exposure time. In the area of physical oceanography, experiments using these water bodies as a natural laboratory and interpreting their circulation and mixing processes using theoretical and semi-theoretical knowledge are of fundamental importance. Small-scale physical models may also be used together with analytical and numerical models. The book highlights the fact that research and theory are interactive, and the results provide the fundamentals for the development of the estuarine research.

  11. Fundamental investigations of catalyst nanoparticles

    DEFF Research Database (Denmark)

    Elkjær, Christian Fink

    area Cu=ZnO=Al2O3 structure that is difficult to study by TEM. We therefore created size-selected CuZn alloy nanoparticles that were transformed by oxidation and reduction into Cu nanoparticles decorated with ZnO. This represents a simplified model system for the high surface area catalyst...... been unknown. We used nanoreactor technology which allows for simultaneous TEM imaging and activity measurement, also referred to as an Operando experiment. With this we revealed that the shape of the Pt nanoparticles changed in phase with changes in global reaction rate. By the use of reactor modeling...... fundamental understanding of catalytic processes and our ability to make use of that understanding. This thesis presents fundamental studies of catalyst nanoparticles with particular focus on dynamic processes. Such studies often require atomic-scale characterization, because the catalytic conversion takes...

  12. Unified Theory of Fundamental Interactions

    Institute of Scientific and Technical Information of China (English)

    WU Ning

    2003-01-01

    Based on local gauge invariance, four different kinds of fundamental interactions in nature are unified in a theory which has SU(3)C( )SU SU(2)L( )U(1)( )s Gravitational Gauge Group gauge symmetry. In this approach,gravitational field, like electromagnetic field, intermediate gauge field, and gluon field, is represented by gauge potential.Four kinds of fundamental interactions are formulated in the similar manner, and therefore can be unified in a direct or semi-direct product group. The model discussed in this paper is a renormalizable quantum model and can be regarded as an extension of the standard model to gravitational interactions, so it can be used to study quantum effects of gravitational interactions.

  13. Astrophysical Probes of Fundamental Physics

    CERN Document Server

    Martins, C J A P

    2006-01-01

    I review the theoretical motivation for varying fundamental couplings and discuss how these measurements can be used to constrain a number of fundamental physics scenarios that would otherwise be inacessible to experiment. As a case study I will focus on the relation between varying couplings and dark energy, and explain how varying coupling measurements can be used to probe the nature of dark energy, with important advantages over the standard methods. Assuming that the current observational evidence for varying $\\alpha$ and $\\mu$ is correct, a several-sigma detection of dynamical dark energy is feasible within a few years, using currently operational ground-based facilities. With forthcoming instruments like CODEX, a high-accuracy reconstruction of the equation of state may be possible all the way up to redshift $z\\sim4$.

  14. Fundamentals of condensed matter physics

    CERN Document Server

    Cohen, Marvin L

    2016-01-01

    Based on an established course and covering the fundamentals, central areas, and contemporary topics of this diverse field, Fundamentals of Condensed Matter Physics is a much-needed textbook for graduate students. The book begins with an introduction to the modern conceptual models of a solid from the points of view of interacting atoms and elementary excitations. It then provides students with a thorough grounding in electronic structure as a starting point to understand many properties of condensed matter systems - electronic, structural, vibrational, thermal, optical, transport, magnetic and superconductivity - and methods to calculate them. Taking readers through the concepts and techniques, the text gives both theoretically and experimentally inclined students the knowledge needed for research and teaching careers in this field. It features 200 illustrations, 40 worked examples and 150 homework problems for students to test their understanding. Solutions to the problems for instructors are available at w...

  15. Fundamental neutron physics at LANSCE

    Energy Technology Data Exchange (ETDEWEB)

    Greene, G.

    1995-10-01

    Modern neutron sources and science share a common origin in mid-20th-century scientific investigations concerned with the study of the fundamental interactions between elementary particles. Since the time of that common origin, neutron science and the study of elementary particles have evolved into quite disparate disciplines. The neutron became recognized as a powerful tool for studying condensed matter with modern neutron sources being primarily used (and justified) as tools for neutron scattering and materials science research. The study of elementary particles has, of course, led to the development of rather different tools and is now dominated by activities performed at extremely high energies. Notwithstanding this trend, the study of fundamental interactions using neutrons has continued and remains a vigorous activity at many contemporary neutron sources. This research, like neutron scattering research, has benefited enormously by the development of modern high-flux neutron facilities. Future sources, particularly high-power spallation sources, offer exciting possibilities for continuing this research.

  16. THE FUNDAMENTS OF EXPLANATORY CAUSES

    Directory of Open Access Journals (Sweden)

    Lavinia Mihaela VLĂDILĂ

    2015-07-01

    Full Text Available The new Criminal Code in the specter of the legal life the division of causes removing the criminal feature of the offence in explanatory causes and non-attributable causes. This dichotomy is not without legal and factual fundaments and has been subjected to doctrinaire debates even since the period when the Criminal Code of 1969 was still in force. From our perspective, one of the possible legal fundaments of the explanatory causes results from that the offence committed is based on the protection of a right at least equal with the one prejudiced by the action of aggression, salvation, by the legal obligation imposed or by the victim’s consent.

  17. Modern measurements fundamentals and applications

    CERN Document Server

    Petri, D; Carbone, P; Catelani, M

    2015-01-01

    This book explores the modern role of measurement science for both the technically most advanced applications and in everyday and will help readers gain the necessary skills to specialize their knowledge for a specific field in measurement. Modern Measurements is divided into two parts. Part I (Fundamentals) presents a model of the modern measurement activity and the already recalled fundamental bricks. It starts with a general description that introduces these bricks and the uncertainty concept. The next chapters provide an overview of these bricks and finishes (Chapter 7) with a more general and complex model that encompasses both traditional (hard) measurements and (soft) measurements, aimed at quantifying non-physical concepts, such as quality, satisfaction, comfort, etc. Part II (Applications) is aimed at showing how the concepts presented in Part I can be usefully applied to design and implement measurements in some very impor ant and broad fields. The editors cover System Identification (Chapter 8...

  18. Fundamental Scaling Laws in Nanophotonics

    OpenAIRE

    Ke Liu; Shuai Sun; Arka Majumdar; Volker J. Sorger

    2016-01-01

    The success of information technology has clearly demonstrated that miniaturization often leads to unprecedented performance, and unanticipated applications. This hypothesis of “smaller-is-better” has motivated optical engineers to build various nanophotonic devices, although an understanding leading to fundamental scaling behavior for this new class of devices is missing. Here we analyze scaling laws for optoelectronic devices operating at micro and nanometer length-scale. We show that optoe...

  19. Variation of fundamental constants: theory

    Science.gov (United States)

    Flambaum, Victor

    2008-05-01

    Theories unifying gravity with other interactions suggest temporal and spatial variation of the fundamental ``constants'' in expanding Universe. There are some hints for the variation of different fundamental constants in quasar absorption spectra and Big Bang nucleosynthesis data. A large number of publications (including atomic clocks) report limits on the variations. We want to study the variation of the main dimensionless parameters of the Standard Model: 1. Fine structure constant alpha (combination of speed of light, electron charge and Plank constant). 2. Ratio of the strong interaction scale (LambdaQCD) to a fundamental mass like electron mass or quark mass which are proportional to Higgs vacuum expectation value. The proton mass is propotional to LambdaQCD, therefore, the proton-to-electron mass ratio comes into this second category. We performed necessary atomic, nuclear and QCD calculations needed to study variation of the fundamental constants using the Big Bang Nucleosynthsis, quasar spectra, Oklo natural nuclear reactor and atomic clock data. The relative effects of the variation may be enhanced in transitions between narrow close levels in atoms, molecules and nuclei. If one will study an enhanced effect, the relative value of systematic effects (which are not enhanced) may be much smaller. Note also that the absolute magnitude of the variation effects in nuclei (e.g. in very narrow 7 eV transition in 229Th) may be 5 orders of magnitude larger than in atoms. A different possibility of enhancement comes from the inversion transitions in molecules where splitting between the levels is due to the quantum tunneling amplitude which has strong, exponential dependence on the electron to proton mass ratio. Our study of NH3 quasar spectra has already given the best limit on the variation of electron to proton mass ratio.

  20. Fundamentals of plastic optical fibers

    CERN Document Server

    Koike, Yasuhiro

    2014-01-01

    Polymer photonics is an interdisciplinary field which demands excellence both in optics (photonics) and materials science (polymer). However, theses disciplines have developed independently, and therefore the demand for a comprehensive work featuring the fundamentals of photonic polymers is greater than ever.This volume focuses on Polymer Optical Fiber and their applications. The first part of the book introduces typical optical fibers according to their classifications of material, propagating mode, and structure. Optical properties, the high bandwidth POF and transmission loss are discussed,

  1. Fundamentals of spatial information systems

    CERN Document Server

    Laurini, Robert

    1992-01-01

    The study and application of spatial information systems have been developed primarily from the use of computers in the geosciences. These systems have the principle functions of capturing, storing, representing, manipulating, and displaying data in 2-D and 3-D worlds. This book approaches its subject from the perspectives of informatics and geography, presenting methods of conceptual modeling developed in computer science that provide valuable aids for resolving spatial problems. This book is an essential textbook for both students and practitioners. It is indispensable for academic geographe

  2. Cholesterol-Induced Suppression of Membrane Elastic Fluctuations at the Atomistic Level

    Science.gov (United States)

    Molugu, Trivikram R.

    2017-01-01

    Applications of solid-state NMR spectroscopy for investigating the influences of lipid-cholesterol interactions on membrane fluctuations are reviewed in this paper. Emphasis is placed on understanding the energy landscapes and fluctuations at an emergent atomistic level. Solid-state 2H NMR spectroscopy directly measures residual quadrupolar couplings (RQCs) due to individual C–2H labeled segments of the lipid molecules. Moreover, residual dipolar couplings (RDCs) of 13C–1H bonds are obtained in separated local-field NMR spectroscopy. The distributions of RQC or RDC values give nearly complete profiles of the order parameters as a function of acyl segment position. Measured equilibrium properties of glycerophospholipids and sphingolipids including their binary and tertiary mixtures with cholesterol show unequal mixing associated with liquid-ordered domains. The entropic loss upon addition of cholesterol to sphingolipids is less than for glycerophospholipids and may drive the formation of lipid rafts. In addition relaxation time measurements enable one to study the molecular dynamics over a wide time-scale range. For 2H NMR the experimental spin-lattice (R1Z) relaxation rates follow a theoretical square-law dependence on segmental order parameters (SCD) due to collective slow dynamics over mesoscopic length scales. The functional dependence for the liquid-crystalline lipid membranes is indicative of viscoelastic properties as they emerge from atomistic-level interactions. A striking decrease in square-law slope upon addition of cholesterol denotes stiffening relative to the pure lipid bilayers that is diminished in the case of lanosterol. Measured equilibrium properties and relaxation rates infer opposite influences of cholesterol and detergents on collective dynamics and elasticity at an atomistic scale that potentially affects lipid raft formation in cellular membranes. PMID:27154600

  3. Cholesterol-induced suppression of membrane elastic fluctuations at the atomistic level.

    Science.gov (United States)

    Molugu, Trivikram R; Brown, Michael F

    2016-09-01

    Applications of solid-state NMR spectroscopy for investigating the influences of lipid-cholesterol interactions on membrane fluctuations are reviewed in this paper. Emphasis is placed on understanding the energy landscapes and fluctuations at an emergent atomistic level. Solid-state (2)H NMR spectroscopy directly measures residual quadrupolar couplings (RQCs) due to individual C-(2)H labeled segments of the lipid molecules. Moreover, residual dipolar couplings (RDCs) of (13)C-(1)H bonds are obtained in separated local-field NMR spectroscopy. The distributions of RQC or RDC values give nearly complete profiles of the order parameters as a function of acyl segment position. Measured equilibrium properties of glycerophospholipids and sphingolipids including their binary and tertiary mixtures with cholesterol show unequal mixing associated with liquid-ordered domains. The entropic loss upon addition of cholesterol to sphingolipids is less than for glycerophospholipids and may drive the formation of lipid rafts. In addition relaxation time measurements enable one to study the molecular dynamics over a wide time-scale range. For (2)H NMR the experimental spin-lattice (R1Z) relaxation rates follow a theoretical square-law dependence on segmental order parameters (SCD) due to collective slow dynamics over mesoscopic length scales. The functional dependence for the liquid-crystalline lipid membranes is indicative of viscoelastic properties as they emerge from atomistic-level interactions. A striking decrease in square-law slope upon addition of cholesterol denotes stiffening relative to the pure lipid bilayers that is diminished in the case of lanosterol. Measured equilibrium properties and relaxation rates infer opposite influences of cholesterol and detergents on collective dynamics and elasticity at an atomistic scale that potentially affects lipid raft formation in cellular membranes.

  4. Using a scalar parameter to trace dislocation evolution in atomistic modeling

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jinbo [ORNL; Zhang, Z F [Shenyang National Laboratory for Materials Science; Osetskiy, Yury N [ORNL; Stoller, Roger E [ORNL

    2015-01-01

    A scalar gamma-parameter is proposed from the Nye tensor. Its maximum value occurs along a dislocation line, either straight or curved, when the coordinate system is purposely chosen. This parameter can be easily obtained from the Nye tensor calculated at each atom in atomistic modeling. Using the gamma-parameter, a fully automated approach is developed to determine core atoms and the Burgers vectors of dislocations simultaneously. The approach is validated by revealing the smallest dislocation loop and by tracing the whole formation process of complicated dislocation networks on the fly.

  5. Electron and phonon transport in silicon nanowires: Atomistic approach to thermoelectric properties

    DEFF Research Database (Denmark)

    Markussen, Troels; Jauho, Antti-Pekka; Brandbyge, Mads

    2009-01-01

    We compute both electron and phonon transmissions in thin disordered silicon nanowires (SiNWs). Our atomistic approach is based on tight-binding and empirical potential descriptions of the electronic and phononic systems, respectively. Surface disorder is modeled by introducing surface silicon...... apply this averaging method to surface disordered SiNWs in the diameter range of 1–3 nm to compute the thermoelectric figure of merit ZT. It is found that the phonon transmission is affected more by the vacancies than the electronic transmission leading to an increased thermoelectric performance...

  6. Atomistic understanding of hydrogen loading phenomenon into palladium cathode: A simple nanocluster approach and electrochemical evidence

    Indian Academy of Sciences (India)

    Mohsen Lashgari; Davood Matloubi

    2015-03-01

    The inherent potency of palladium to sorb hydrogen atoms was examined empirically and theoretically through various electrochemical methods and high-level quantum chemical calculations (HSE06) based on cluster model (CM) and density functional theory (DFT). The CM-DFT approach using QZVP/cc-PV6Z basis sets revealed a strong attraction between Pd nanoclusters and H atoms that generates some charged entities. This atomistically justifies why the electrochemical impedance of the system becomes less by the loading phenomenon. It is concluded that hydrogen atoms enter the palladium subsurface through hollow and bridge sites by diffusing as proton-like species and get loaded predominantly in the octahedral voids.

  7. Methods for atomistic abrasion simulations of laterally periodic polycrystalline substrates with fractal surfaces

    Science.gov (United States)

    Eder, S. J.; Bianchi, D.; Cihak-Bayr, U.; Gkagkas, K.

    2017-03-01

    In this work we discuss a method to generate laterally periodic polycrystalline samples with fractal surfaces for use in molecular dynamics simulations of abrasion. We also describe a workflow that allows us to produce random lateral distributions of simple but realistically shaped hard abrasive particles with Gaussian size distribution and random particle orientations. We evaluate some on-the-fly analysis and visualization possibilities that may be applied during a molecular dynamics simulation to considerably reduce the post-processing effort. Finally, we elaborate on a parallelizable post-processing approach to evaluating and visualizing the surface topography, the grain structure and orientation, as well as the temperature distribution in large atomistic systems.

  8. Predicting growth of graphene nanostructures using high-fidelity atomistic simulations

    Energy Technology Data Exchange (ETDEWEB)

    McCarty, Keven F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Zhou, Xiaowang [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ward, Donald K. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Schultz, Peter A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Foster, Michael E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bartelt, Norman Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-09-01

    In this project we developed t he atomistic models needed to predict how graphene grows when carbon is deposited on metal and semiconductor surfaces. We first calculated energies of many carbon configurations using first principles electronic structure calculations and then used these energies to construct an empirical bond order potentials that enable s comprehensive molecular dynamics simulation of growth. We validated our approach by comparing our predictions to experiments of graphene growth on Ir, Cu and Ge. The robustness of ou r understanding of graphene growth will enable high quality graphene to be grown on novel substrates which will expand the number of potential types of graphene electronic devices.

  9. Atomistic Simulation of Intrinsic Defects and Trivalent and Tetravalent Ion Doping in Hydroxyapatite

    Directory of Open Access Journals (Sweden)

    Ricardo D. S. Santos

    2014-01-01

    Full Text Available Atomistic simulation techniques have been employed in order to investigate key issues related to intrinsic defects and a variety of dopants from trivalent and tetravalent ions. The most favorable intrinsic defect is determined to be a scheme involving calcium and hydroxyl vacancies. It is found that trivalent ions have an energetic preference for the Ca site, while tetravalent ions can enter P sites. Charge compensation is predicted to occur basically via three schemes. In general, the charge compensation via the formation of calcium vacancies is more favorable. Trivalent dopant ions are more stable than tetravalent dopants.

  10. Rotational viscosity of a liquid crystal mixture:a fully atomistic molecular dynamics study

    Institute of Scientific and Technical Information of China (English)

    Zhang Ran; Peng Zeng-Hui; Liu Yong-Gang; Zheng Zhi-Gang; Xuan Li

    2009-01-01

    Fully atomistic molecular dynamics(MD)simulations at 293, 303 and 313 K have been performed for the four. component liquid crystal mixture, E7, using the software package Material Studio. Order parameters and orientational time correlation functions(TCFs)were calculated from MD trajectories. The rotational viscosity coefficients(RVCs)of the mixture were ca]culated using the Nemtsov-Zakharov and Fialkowski methods based on statistical-mechanical approaches. Temperature dependences of RVC and density were discussed in detall. Reasonable agreement between the simulated and experimental values was found.

  11. Dislocation pinning effects on fracture behavior: Atomistic and dislocation dynamics simulations

    Science.gov (United States)

    Noronha, S. J.; Farkas, D.

    2002-10-01

    We introduce an approach in which results from atomistic simulations are combined with discrete dislocation dynamics simulations of crack-tip plasticity. The method is used to study the effects of dislocation pinning due to grain boundaries or secondary particles on the fracture behavior of aluminum. We find that the fracture resistance is reduced with decreasing pinning distance. The results show that the pinning of the dislocations causes a net decrease in the shear stress projected on the slip plane, preventing further dislocation emission. Semibrittle cleavage occurs after a certain number of dislocations is emitted.

  12. Investigations on the mechanical behavior of nanowires with twin boundaries by atomistic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Xia, E-mail: tianxia@lsec.cc.ac.cn [College of Mechanics and Materials, HoHai University, Nanjing 210098 (China)

    2015-03-10

    Atomistic simulations are used to study the deformation behavior of twinned Cu nanowires with a <111> growth orientation under tension. Due to the existence of the twin boundaries, the strength of the twinned nanowires is higher than that of the twin-free nanowire and the yielding stress of twinned nanowires is inversely proportional to the spacings of the twin boundaries. Moreover, The ductility of the twin-free nanowire is the highest of all and it grows with the increasing spacings of the twin boundaries for twinned nanowires. Besides, we find that the twin boundaries can be served as dislocation sources as well as the free surfaces and grain boundaries.

  13. Elastic behavior of amorphous-crystalline silicon nanocomposite: An atomistic view

    Science.gov (United States)

    Das, Suvankar; Dutta, Amlan

    2017-01-01

    In the context of mechanical properties, nanocomposites with homogeneous chemical composition throughout the matrix and the dispersed phase are of particular interest. In this study, the elastic moduli of amorphous-crystalline silicon nanocomposite have been estimated using atomistic simulations. A comparison with the theoretical model reveals that the elastic behavior is significantly influenced by the crystal-amorphous interphase. On observing the effect of volume-fraction of the crystalline phase, an anomalous trend for the bulk modulus is obtained. This phenomenon is attributed to the relaxation displacements of the amorphous atoms.

  14. Atomistic spin dynamic method with both damping and moment of inertia effects included from first principles.

    Science.gov (United States)

    Bhattacharjee, Satadeep; Nordström, Lars; Fransson, Jonas

    2012-02-03

    We consider spin dynamics for implementation in an atomistic framework and we address the feasibility of capturing processes in the femtosecond regime by inclusion of moment of inertia. In the spirit of an s-d-like interaction between the magnetization and electron spin, we derive a generalized equation of motion for the magnetization dynamics in the semiclassical limit, which is nonlocal in both space and time. Using this result we retain a generalized Landau-Lifshitz-Gilbert equation, also including the moment of inertia, and demonstrate how the exchange interaction, damping, and moment of inertia, all can be calculated from first principles.

  15. Atomistic formulas for local properties in systems with many-body interactions

    Science.gov (United States)

    Hardy, Robert J.

    2016-11-01

    Atomistic formulas are derived for the local densities and fluxes used in the continuum description of energy and momentum transport. Two general methods for the distribution of potential energy among a system's constituent particles are presented and analyzed. The resulting formulas for the heat flux and stress tensor and the equations for energy and momentum transport are exact consequences of the definitions of the densities and the equations of classical mechanics. The formulas and equations obtained are valid for systems with very general types of many-body interactions.

  16. Cold melting of beryllium: Atomistic view on Z-machine experiments

    Science.gov (United States)

    Dremov, V. V.; Rykounov, A. A.; Sapozhnikov, F. A.; Karavaev, A. V.; Yakovlev, S. V.; Ionov, G. V.; Ryzhkov, M. V.

    2015-07-01

    Analysis of phase diagram of beryllium at high pressures and temperatures obtained as a result of ab initio calculations and large scale classical molecular dynamics simulations of beryllium shock loading have shown that the so called cold melting takes place when shock wave propagates through polycrystalline samples. Comparison of ab initio calculation results on sound speed along the Hugoniot with experimental data obtained on Z-machine also evidences for possible manifestation of the cold melting. The last may explain the discrepancy between atomistic simulations and experimental data on the onset of the melting on the Hugoniot.

  17. Intelligent hearing aids: the next revolution.

    Science.gov (United States)

    Tao Zhang; Mustiere, Fred; Micheyl, Christophe

    2016-08-01

    The first revolution in hearing aids came from nonlinear amplification, which allows better compensation for both soft and loud sounds. The second revolution stemmed from the introduction of digital signal processing, which allows better programmability and more sophisticated algorithms. The third revolution in hearing aids is wireless, which allows seamless connectivity between a pair of hearing aids and with more and more external devices. Each revolution has fundamentally transformed hearing aids and pushed the entire industry forward significantly. Machine learning has received significant attention in recent years and has been applied in many other industries, e.g., robotics, speech recognition, genetics, and crowdsourcing. We argue that the next revolution in hearing aids is machine intelligence. In fact, this revolution is already quietly happening. We will review the development in at least three major areas: applications of machine learning in speech enhancement; applications of machine learning in individualization and customization of signal processing algorithms; applications of machine learning in improving the efficiency and effectiveness of clinical tests. With the advent of the internet of things, the above developments will accelerate. This revolution will bring patient satisfactions to a new level that has never been seen before.

  18. Consistent Energy-Based Atomistic/Continuum Coupling for Two-Body Potential: 1D and 2D Case

    CERN Document Server

    Shapeev, Alexander V

    2010-01-01

    This paper concerns the problem of consistent energy-based coupling of atomistic and continuum models of materials, limited to zero-temperature statics of simple crystalline materials. It has been widely recognized that the most practical coupled methods exhibit finite errors on the atomistic/continuum interface (which are often attributed to spurious forces called "ghost forces"). There are only few existing works that propose a coupling which is sufficiently accurate near the interface under certain limitations. In this paper a novel coupling that is free from "ghost forces" is proposed for a two-body interaction potential under the assumptions of either (i) one spatial dimension, or (ii) two spatial dimensions and piecewise affine finite elements for describing the continuum deformation. The computational efficiency of the proposed coupling is demonstrated with numerical experiments. The coupling strategy is based on judiciously defining the contributions of the atomistic bonds to the discrete and the cont...

  19. Magnetic Implants Aid Hearing

    Institute of Scientific and Technical Information of China (English)

    陈宏

    1995-01-01

    The next generation of hearing aids may use tiny magnets that fit inside the ear. Researchersat a California company and an engineer at the University of Virginia are both developing systems that rely on magnets to convey sounds. Conventional hearing aids have three components:a microphone, an amplifier, and a speaker. The microphone picks up sounds and sends them to the am-

  20. Genetic Immunity to AIDS

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    In an article on genetic immunity to AIDS published in Science magazine, American and Chinese scientists claim to have discovered why certain HIV carriers do not develop full-blown AIDS. They say that the key to this conundrum lies in a particular protein in the endocrine system that inhibits development of HIV.

  1. Aid and sectoral growth

    DEFF Research Database (Denmark)

    Selaya, Pablo; Thiele, Rainer

    2010-01-01

    This article examines empirically the proposition that aid to poor countries is detrimental for external competitiveness, giving rise to Dutch disease type effects. At the aggregate level, aid is found to have a positive effect on growth. A sectoral decomposition shows that the effect is (i...

  2. International Aid to Education

    Science.gov (United States)

    Benavot, Aaron

    2010-01-01

    Recent evidence highlights several worrisome trends regarding aid pledges and disbursements, which have been exacerbated by the global financial crisis. First, while overall development assistance rose in 2008, after 2 years of decline, the share of all sector aid going to the education sector has remained virtually unchanged at about 12 percent…

  3. AIDS Epidemiological models

    Science.gov (United States)

    Rahmani, Fouad Lazhar

    2010-11-01

    The aim of this paper is to present mathematical modelling of the spread of infection in the context of the transmission of the human immunodeficiency virus (HIV) and the acquired immune deficiency syndrome (AIDS). These models are based in part on the models suggested in the field of th AIDS mathematical modelling as reported by ISHAM [6].

  4. Aid and Income

    DEFF Research Database (Denmark)

    Lof, Matthijs; Mekasha, Tseday Jemaneh; Tarp, Finn

    2015-01-01

    to nonrandom omission of a large proportion of observations. Furthermore, we show that NDHKM’s use of co-integrated regressions is not a suitable empirical strategy for estimating the causal effect of aid on income. Evidence from a Panel VAR model estimated on the dataset of NDHKM, suggests a positive...... and statistically significant long-run effect of aid on income....

  5. First Aid: Burns

    Science.gov (United States)

    ... Your 1- to 2-Year-Old First Aid: Burns KidsHealth > For Parents > First Aid: Burns A A A Scald burns from hot water and other liquids are the most common burns in early childhood. Because burns range from mild ...

  6. The Aid Effectiveness Literature

    DEFF Research Database (Denmark)

    Doucouliagos, Hristos; Paldam, Martin

    The AEL consists of empirical macro studies of the effects of development aid. At the end of 2004 it had reached 97 studies of three families, which we have summarized in one study each using meta-analysis. Studies of the effect on investments show that they rise by 1/3 of the aid – the rest is c...

  7. First Aid: Diaper Rash

    Science.gov (United States)

    ... Your 1- to 2-Year-Old First Aid: Diaper Rash KidsHealth > For Parents > First Aid: Diaper Rash A A A Diaper rash is a common skin condition in babies. ... rash is due to irritation caused by the diaper, but it can have other causes not related ...

  8. First Aid: Burns

    Science.gov (United States)

    ... Old Feeding Your 8- to 12-Month-Old Feeding Your 1- to 2-Year-Old First Aid: Burns KidsHealth > For Parents > First Aid: Burns Print A A A Scald burns from hot water and other liquids are the most common burns in early childhood. Because burns range from mild to life threatening, ...

  9. Aid, Development, and Education

    Science.gov (United States)

    Klees, Steven J.

    2010-01-01

    The world faces pervasive poverty and inequality. Hundreds of billions of dollars in international aid have been given or loaned to developing countries though bilateral and multilateral mechanisms, at least, ostensibly, in order to do something about these problems. Has such aid helped? Debates around this question have been ongoing for decades,…

  10. HIV and AIDS

    Science.gov (United States)

    ... one HIV test by the time they are teens. If you are having sex, have had sex in the past, or shared ... reviewed: October 2015 previous 1 • 2 • ... STDs How Do People Get AIDS? Can You Get HIV From Having Sex With Someone Who Has AIDS? Can Someone Get ...

  11. First Aid: Falls

    Science.gov (United States)

    ... Your 1- to 2-Year-Old First Aid: Falls KidsHealth > For Parents > First Aid: Falls Print A A A en español Folleto de instructiones: Caídas (Falls) With all the running, climbing, and exploring kids ...

  12. AIDS as Metaphor.

    Science.gov (United States)

    McMillen, Liz

    1994-01-01

    Scholarly interest in Acquired Immune Deficiency Syndrome (AIDS) has spread throughout the humanities, attracting the attention of historians of medicine, political scientists, sociologists, public health scholars, and anthropologists. Most theorists hope their research will aid in policymaking or change understanding of the epidemic. (MSE)

  13. A neglected epidemic: fungal infections in HIV/AIDS.

    Science.gov (United States)

    Armstrong-James, Darius; Meintjes, Graeme; Brown, Gordon D

    2014-03-01

    Invasive fungal infections (IFIs) are a major cause of HIV-related mortality globally. Despite widespread rollout of combined antiretroviral therapy, there are still up to 1 million deaths annually from IFIs, accounting for 50% of all AIDS-related death. A historic failure to focus efforts on the IFIs that kill so many HIV patients has led to fundamental flaws in the management of advanced HIV infection. This review, based on the EMBO AIDS-Related Mycoses Workshop in Cape Town in July 2013, summarizes the current state of the-art in AIDS-related mycoses, and the key action points required to improve outcomes from these devastating infections.

  14. Fundamental Limits to Cellular Sensing

    Science.gov (United States)

    ten Wolde, Pieter Rein; Becker, Nils B.; Ouldridge, Thomas E.; Mugler, Andrew

    2016-03-01

    In recent years experiments have demonstrated that living cells can measure low chemical concentrations with high precision, and much progress has been made in understanding what sets the fundamental limit to the precision of chemical sensing. Chemical concentration measurements start with the binding of ligand molecules to receptor proteins, which is an inherently noisy process, especially at low concentrations. The signaling networks that transmit the information on the ligand concentration from the receptors into the cell have to filter this receptor input noise as much as possible. These networks, however, are also intrinsically stochastic in nature, which means that they will also add noise to the transmitted signal. In this review, we will first discuss how the diffusive transport and binding of ligand to the receptor sets the receptor correlation time, which is the timescale over which fluctuations in the state of the receptor, arising from the stochastic receptor-ligand binding, decay. We then describe how downstream signaling pathways integrate these receptor-state fluctuations, and how the number of receptors, the receptor correlation time, and the effective integration time set by the downstream network, together impose a fundamental limit on the precision of sensing. We then discuss how cells can remove the receptor input noise while simultaneously suppressing the intrinsic noise in the signaling network. We describe why this mechanism of time integration requires three classes (groups) of resources—receptors and their integration time, readout molecules, energy—and how each resource class sets a fundamental sensing limit. We also briefly discuss the scheme of maximum-likelihood estimation, the role of receptor cooperativity, and how cellular copy protocols differ from canonical copy protocols typically considered in the computational literature, explaining why cellular sensing systems can never reach the Landauer limit on the optimal trade

  15. Fundamental cycles and graph embeddings

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In this paper, we investigate fundamental cycles in a graph G and their relations with graph embeddings. We show that a graph G may be embedded in an orientable surface with genus at least g if and only if for any spanning tree T , there exists a sequence of fundamental cycles C1, C2, . . . , C2g with C2i-1 ∩ C2i≠ф for 1≤ i ≤g. In particular, among β(G) fundamental cycles of any spanning tree T of a graph G, there are exactly 2γM (G) cycles C1, C2, . . . , C2γM (G) such that C2i-1 ∩ C2i≠ф for 1 ≤i≤γM (G), where β(G) and γM (G) are the Betti number and the maximum genus of G, respectively. This implies that it is possible to construct an orientable embedding with large genus of a graph G from an arbitrary spanning tree T (which may have very large number of odd components in G\\E(T )). This is different from the earlier work of Xuong and Liu, where spanning trees with small odd components are needed. In fact, this makes a common generalization of Xuong, Liu and Fu et al. Furthermore, we show that (1) this result is useful for locating the maximum genus of a graph having a specific edge-cut. Some known results for embedded graphs are also concluded; (2) the maximum genus problem may be reduced to the maximum matching problem. Based on this result and the algorithm of Micali-Vazirani, we present a new efficient algorithm to determine the maximum genus of a graph in O((β(G)) 25 ) steps. Our method is straight and quite different from the algorithm of Furst, Gross and McGeoch which depends on a result of Giles where matroid parity method is needed.

  16. Fundamentals of gas particle flow

    CERN Document Server

    Rudinger, G

    1980-01-01

    Fundamentals of Gas-Particle Flow is an edited, updated, and expanded version of a number of lectures presented on the "Gas-Solid Suspensions” course organized by the von Karman Institute for Fluid Dynamics. Materials presented in this book are mostly analytical in nature, but some experimental techniques are included. The book focuses on relaxation processes, including the viscous drag of single particles, drag in gas-particles flow, gas-particle heat transfer, equilibrium, and frozen flow. It also discusses the dynamics of single particles, such as particles in an arbitrary flow, in a r

  17. Fundamentals of magnetism and electricity

    CERN Document Server

    Arya, SN

    2009-01-01

    Fundamentals of Magnetism and Electricity is a textbook on the physics of electricity, magnetism, and electromagnetic fields and waves. It is written mainly with the physics student in mind, although it will also be of use to students of electrical and electronic engineering. The approach is concise but clear, and the author has assumed that the reader will be familiar with the basic phenomena. The theory, however, is set out in a completely self-contained and coherent way and developed to the point where the reader can appreciate the beauty and coherence of the Maxwell equations.

  18. Electronic imaging fundamentals: basic theory.

    Science.gov (United States)

    Vizy, K N

    1983-01-01

    Introduction of the computer into the field of medical imaging, as typified by the extensive use of digital subtraction angiography (DSA), created an important need for a basic understanding of the principles of digital imaging. This paper reviews these fundamental principles, starting with the definition of images and the interaction of these images with television display systems, then continuing with a detailed description of the way in which imaging systems are specified. This work defines the basic terms and concepts that will be used throughout the contents of this issue.

  19. Quantum Uncertainty and Fundamental Interactions

    Directory of Open Access Journals (Sweden)

    Tosto S.

    2013-04-01

    Full Text Available The paper proposes a simplified theoretical approach to infer some essential concepts on the fundamental interactions between charged particles and their relative strengths at comparable energies by exploiting the quantum uncertainty only. The worth of the present approach relies on the way of obtaining the results, rather than on the results themselves: concepts today acknowledged as fingerprints of the electroweak and strong interactions appear indeed rooted in the same theoretical frame including also the basic principles of special and general relativity along with the gravity force.

  20. Fundamental Laser Welding Process Investigations

    DEFF Research Database (Denmark)

    Bagger, Claus; Olsen, Flemming Ove

    1998-01-01

    In a number of systematic laboratory investigations the fundamental behavior of the laser welding process was analyzed by the use of normal video (30 Hz), high speed video (100 and 400 Hz) and photo diodes. Sensors were positioned to monitor the welding process from both the top side and the rear...... side of the specimen.Special attention has been given to the dynamic nature of the laser welding process, especially during unstable welding conditions. In one series of experiments, the stability of the process has been varied by changing the gap distance in lap welding. In another series...

  1. Communication technology update and fundamentals

    CERN Document Server

    Grant, August E

    2014-01-01

    A classic now in its 14th edition, Communication Technology Update and Fundamentals is the single best resource for students and professionals looking to brush up on how these technologies have developed, grown, and converged, as well as what's in store for the future. It begins by developing the communication technology framework-the history, ecosystem, and structure-then delves into each type of technology, including everything from mass media, to computers and consumer electronics, to networking technologies. Each chapter is written by faculty and industry experts who p

  2. Foam engineering fundamentals and applications

    CERN Document Server

    2012-01-01

    Containing contributions from leading academic and industrial researchers, this book provides a much needed update of foam science research. The first section of the book presents an accessible summary of the theory and fundamentals of foams. This includes chapters on morphology, drainage, Ostwald ripening, coalescence, rheology, and pneumatic foams. The second section demonstrates how this theory is used in a wide range of industrial applications, including foam fractionation, froth flotation and foam mitigation. It includes chapters on suprafroths, flotation of oil sands, foams in enhancing petroleum recovery, Gas-liquid Mass Transfer in foam, foams in glass manufacturing, fire-fighting foam technology and consumer product foams.

  3. Computing fundamentals digital literacy edition

    CERN Document Server

    Wempen, Faithe

    2014-01-01

    Computing Fundamentals has been tailor made to help you get up to speed on your Computing Basics and help you get proficient in entry level computing skills. Covering all the key topics, it starts at the beginning and takes you through basic set-up so that you'll be competent on a computer in no time.You'll cover: Computer Basics & HardwareSoftwareIntroduction to Windows 7Microsoft OfficeWord processing with Microsoft Word 2010Creating Spreadsheets with Microsoft ExcelCreating Presentation Graphics with PowerPointConnectivity and CommunicationWeb BasicsNetwork and Internet Privacy and Securit

  4. Fundamentals of spread spectrum modulation

    CERN Document Server

    Ziemer, Rodger E

    2007-01-01

    This lecture covers the fundamentals of spread spectrum modulation, which can be defined as any modulation technique that requires a transmission bandwidth much greater than the modulating signal bandwidth, independently of the bandwidth of the modulating signal. After reviewing basic digital modulation techniques, the principal forms of spread spectrum modulation are described. One of the most important components of a spread spectrum system is the spreading code, and several types and their characteristics are described. The most essential operation required at the receiver in a spread spect

  5. Fundamentals of soft matter science

    CERN Document Server

    Hirst, Linda S

    2012-01-01

    ""The publication is written at a very fundamental level, which will make it easily readable for undergraduate students. It will certainly also be a valuable text for students and postgraduates in interdisciplinary programmes, as not only physical aspects, but also the chemistry and applications are presented and discussed. … The book is well illustrated, and I really do like the examples and pictures provided for simple demonstration experiments, which can be done during the lectures. Also, the experimental techniques chapter at the end of the book may be helpful. The question sections are he

  6. Computing fundamentals introduction to computers

    CERN Document Server

    Wempen, Faithe

    2014-01-01

    The absolute beginner's guide to learning basic computer skills Computing Fundamentals, Introduction to Computers gets you up to speed on basic computing skills, showing you everything you need to know to conquer entry-level computing courses. Written by a Microsoft Office Master Instructor, this useful guide walks you step-by-step through the most important concepts and skills you need to be proficient on the computer, using nontechnical, easy-to-understand language. You'll start at the very beginning, getting acquainted with the actual, physical machine, then progress through the most common

  7. Fundamentals of ultrasonic phased arrays

    CERN Document Server

    Schmerr, Lester W

    2014-01-01

    This book describes in detail the physical and mathematical foundations of ultrasonic phased array measurements.?The book uses linear systems theory to develop a comprehensive model of the signals and images that can be formed with phased arrays. Engineers working in the field of ultrasonic nondestructive evaluation (NDE) will find in this approach a wealth of information on how to design, optimize and interpret ultrasonic inspections with phased arrays. The fundamentals and models described in the book will also be of significant interest to other fields, including the medical ultrasound and

  8. Solid Lubrication Fundamentals and Applications

    Science.gov (United States)

    Miyoshi, Kazuhisa

    2001-01-01

    Solid Lubrication Fundamentals and Applications description of the adhesion, friction, abrasion, and wear behavior of solid film lubricants and related tribological materials, including diamond and diamond-like solid films. The book details the properties of solid surfaces, clean surfaces, and contaminated surfaces as well as discussing the structures and mechanical properties of natural and synthetic diamonds; chemical-vapor-deposited diamond film; surface design and engineering toward wear-resistant, self-lubricating diamond films and coatings. The author provides selection and design criteria as well as applications for synthetic and natural coatings in the commercial, industrial and aerospace industries..

  9. Photovoltaics fundamentals, technology and practice

    CERN Document Server

    Mertens, Konrad

    2013-01-01

    Concise introduction to the basic principles of solar energy, photovoltaic systems, photovoltaic cells, photovoltaic measurement techniques, and grid connected systems, overviewing the potential of photovoltaic electricity for students and engineers new to the topic After a brief introduction to the topic of photovoltaics' history and the most important facts, Chapter 1 presents the subject of radiation, covering properties of solar radiation, radiation offer, and world energy consumption. Chapter 2 looks at the fundamentals of semiconductor physics. It discusses the build-up of semiconducto

  10. Fundamental Limits of Ultrathin Metasurfaces

    CERN Document Server

    Arbabi, Amir

    2014-01-01

    We present universal theoretical limits on the operation and performance of non-magnetic passive ultrathin metasurfaces. In particular, we prove that their local transmission, reflection, and polarization conversion coefficients are confined to limited regions of the complex plane. As a result, full control over the phase of the light transmitted through such metasurfaces cannot be achieved if the polarization of the light is not to be affected at the same time. We also establish fundamental limits on the maximum polarization conversion efficiency of these metasurfaces, and show that they cannot achieve more than 25% polarization conversion efficiency in transmission.

  11. Fundamentals of liquid crystal devices

    CERN Document Server

    Yang, Deng-Ke

    2014-01-01

    Revised throughout to cover the latest developments in the fast moving area of display technology, this 2nd edition of Fundamentals of Liquid Crystal Devices, will continue to be a valuable resource for those wishing to understand the operation of liquid crystal displays. Significant updates include new material on display components, 3D LCDs and blue-phase displays which is one of the most promising new technologies within the field of displays and it is expected that this new LC-technology will reduce the response time and the number of optical components of LC-modules. Prof. Yang is a pion

  12. Autodesk Combustion 4 fundamentals courseware

    CERN Document Server

    Autodesk,

    2005-01-01

    Whether this is your first experience with Combustion software or you're upgrading to take advantage of the many new features and tools, this guide will serve as your ultimate resource to this all-in-one professional compositing application. Much more than a point-and-click manual, this guide explains the principles behind the software, serving as an overview of the package and associated techniques. Written by certified Autodesk training specialists for motion graphic designers, animators, and visual effects artists, Combustion 4 Fundamentals Courseware provides expert advice for all skill le

  13. The Fundamental Manifold of Spheroids

    CERN Document Server

    Zaritsky, D; Zabludoff, A I; Zaritsky, Dennis; Gonzalez, Anthony H.; Zabludoff, Ann I.

    2006-01-01

    We present a unifying empirical description of the structural and kinematic properties of all spheroids embedded in dark matter halos. We find that the stellar spheroidal components of galaxy clusters, which we call cluster spheroids (CSphs) and which are typically one hundred times the size of normal elliptical galaxies, lie on a "fundamental plane" as tight as that defined by ellipticals (rms in effective radius of ~0.07), but that has a different slope. The slope, as measured by the coefficient of the log(sigma) term, declines significantly and systematically between the fundamental planes of ellipticals, brightest cluster galaxies (BCGs), and CSphs.We attribute this decline primarily to a continuous change in M_e/L_e, the mass-to-light ratio within the effective radius r_e, with spheroid scale. The magnitude of the slope change requires that it arises principally from differences in the relative distributions of luminous and dark matter, rather than from stellar population differences such as in age and m...

  14. Field Theory of Fundamental Interactions

    Science.gov (United States)

    Wang, Shouhong; Ma, Tian

    2017-01-01

    First, we present two basic principles, the principle of interaction dynamics (PID) and the principle of representation invariance (PRI). Intuitively, PID takes the variation of the action under energy-momentum conservation constraint. We show that the PID is the requirement of the presence of dark matter and dark energy, the Higgs field and the quark confinement. PRI requires that the SU(N) gauge theory be independent of representations of SU(N). It is clear that PRI is the logic requirement of any gauge theory. With PRI, we demonstrate that the coupling constants for the strong and the weak interactions are the main sources of these two interactions, reminiscent of the electric charge. Second, we emphasize that symmetry principles-the principle of general relativity and the principle of Lorentz invariance and gauge invariance-together with the simplicity of laws of nature, dictate the actions for the four fundamental interactions. Finally, we show that the PID and the PRI, together with the symmetry principles give rise to a unified field model for the fundamental interactions, which is consistent with current experimental observations and offers some new physical predictions. The research is supported in part by the National Science Foundation (NSF) grant DMS-1515024, and by the Office of Naval Research (ONR) grant N00014-15-1-2662.

  15. O que é Psicopatologia Fundamental

    Directory of Open Access Journals (Sweden)

    Manoel Tosta Berlinck

    Full Text Available Se para os romanos, posição significava lugar onde uma pessoa ou coisa estaria colocada, para os gregos, a noção de posição é de natureza muito mais relacional. Da posição determinada pela postura do corpo, diferenciavam pelo menos duas outras: a do historiador, que não inventa, apenas ouviu falar por aí, e a do teatro, que mostrava o corpo humano em um estado natural de pathos (sofrimento. Ao se pensar o psiquismo e o aparelho psíquico como prolongamentos do sistema imunológico e já que, segundo o autor, pathos é sempre somático, a psique é, seguindo a tradição socrática, estritamente corporal. É próprio, pois, à Psicopatologia Fundamental, reconhecer a existência de múltiplas posições corporais-discursivas e reconhecer que aqueles que ocupam outras posições reconheçam a especificidade de sua posição. A partir do conceito de posição, e seus desdobramentos em pathos e logos, o autor desenvolve sua concepção de Psicopatologia Fundamental.

  16. New Developments in the Embedded Statistical Coupling Method: Atomistic/Continuum Crack Propagation

    Science.gov (United States)

    Saether, E.; Yamakov, V.; Glaessgen, E.

    2008-01-01

    A concurrent multiscale modeling methodology that embeds a molecular dynamics (MD) region within a finite element (FEM) domain has been enhanced. The concurrent MD-FEM coupling methodology uses statistical averaging of the deformation of the atomistic MD domain to provide interface displacement boundary conditions to the surrounding continuum FEM region, which, in turn, generates interface reaction forces that are applied as piecewise constant traction boundary conditions to the MD domain. The enhancement is based on the addition of molecular dynamics-based cohesive zone model (CZM) elements near the MD-FEM interface. The CZM elements are a continuum interpretation of the traction-displacement relationships taken from MD simulations using Cohesive Zone Volume Elements (CZVE). The addition of CZM elements to the concurrent MD-FEM analysis provides a consistent set of atomistically-based cohesive properties within the finite element region near the growing crack. Another set of CZVEs are then used to extract revised CZM relationships from the enhanced embedded statistical coupling method (ESCM) simulation of an edge crack under uniaxial loading.

  17. An atomistic model for cross-linked HNBR elastomers used in seals

    Science.gov (United States)

    Molinari, Nicola; Sutton, Adrian; Stevens, John; Mostofi, Arash

    2015-03-01

    Hydrogenated nitrile butadiene rubber (HNBR) is one of the most common elastomeric materials used for seals in the oil and gas industry. These seals sometimes suffer ``explosive decompression,'' a costly problem in which gases permeate a seal at the elevated temperatures and pressures pertaining in oil and gas wells, leading to rupture when the seal is brought back to the surface. The experimental evidence that HNBR and its unsaturated parent NBR have markedly different swelling properties suggests that cross-linking may occur during hydrogenation of NBR to produce HNBR. We have developed a code compatible with the LAMMPS molecular dynamics package to generate fully atomistic HNBR configurations by hydrogenating initial NBR structures. This can be done with any desired degree of cross-linking. The code uses a model of atomic interactions based on the OPLS-AA force-field. We present calculations of the dependence of a number of bulk properties on the degree of cross-linking. Using our atomistic representations of HNBR and NBR, we hope to develop a better molecular understanding of the mechanisms that result in explosive decompression.

  18. Integrating atomistic molecular dynamics simulations, experiments, and network analysis to study protein dynamics

    DEFF Research Database (Denmark)

    Papaleo, Elena

    2015-01-01

    In the last years, we have been observing remarkable improvements in the field of protein dynamics. Indeed, we can now study protein dynamics in atomistic details over several timescales with a rich portfolio of experimental and computational techniques. On one side, this provides us with the pos......In the last years, we have been observing remarkable improvements in the field of protein dynamics. Indeed, we can now study protein dynamics in atomistic details over several timescales with a rich portfolio of experimental and computational techniques. On one side, this provides us...... that we observe and the functional properties of these important cellular machines. To make progresses in this direction, we need to improve the physical models used to describe proteins and solvent in molecular dynamics, as well as to strengthen the integration of experiments and simulations to overcome...... simulations with attention to the effects that can be propagated over long distances and are often associated to important biological functions. In this context, approaches inspired by network analysis can make an important contribution to the analysis of molecular dynamics simulations....

  19. Atomistic protein folding simulations on the submillisecond time scale using worldwide distributed computing.

    Science.gov (United States)

    Pande, Vijay S; Baker, Ian; Chapman, Jarrod; Elmer, Sidney P; Khaliq, Siraj; Larson, Stefan M; Rhee, Young Min; Shirts, Michael R; Snow, Christopher D; Sorin, Eric J; Zagrovic, Bojan

    2003-01-01

    Atomistic simulations of protein folding have the potential to be a great complement to experimental studies, but have been severely limited by the time scales accessible with current computer hardware and algorithms. By employing a worldwide distributed computing network of tens of thousands of PCs and algorithms designed to efficiently utilize this new many-processor, highly heterogeneous, loosely coupled distributed computing paradigm, we have been able to simulate hundreds of microseconds of atomistic molecular dynamics. This has allowed us to directly simulate the folding mechanism and to accurately predict the folding rate of several fast-folding proteins and polymers, including a nonbiological helix, polypeptide alpha-helices, a beta-hairpin, and a three-helix bundle protein from the villin headpiece. Our results demonstrate that one can reach the time scales needed to simulate fast folding using distributed computing, and that potential sets used to describe interatomic interactions are sufficiently accurate to reach the folded state with experimentally validated rates, at least for small proteins.

  20. Quantum Thermodynamics: Non-equilibrium 3D Description of an Unbounded System at an Atomistic Level

    Directory of Open Access Journals (Sweden)

    Vittorio Verda

    2010-03-01

    Full Text Available Quantum thermodynamics (QT provides a general framework for the description of non-equilibrium phenomena at any level, particularly the atomistic one. This theory and its dynamical postulate are used here to extend the work reported in previous papers of modeling the storage of hydrogen in an isolated system, by extending the modeling to 3D. The system is prepared in a state with the hydrogen molecules initially far from stable equilibrium after which the system is allowed to relax (evolve to a state of stable equilibrium. The so-called energy eigenvalue problem, which entails a many-body problem that for dilute and moderately dense gases can be solved using virial expansion theory, is used to determine the energy eigenvalues and eigenstates of the system. This information is then used in the nonlinear Beretta equation of motion of QT to determine the evolution of the thermodynamic state of the system as well as the spatial distributions of the hydrogen molecules in time. The results of our simulations provide a quantification of the entropy generated due to irreversibilities at an atomistic level and show in detail the trajectory of the state of the system as the hydrogen molecules, which are initially arranged to be far from the carbon nanotube, spread out in the system and eventually become more concentrated near the carbon atoms which make up the nanotube.

  1. Fully atomistic molecular-mechanical model of liquid alkane oils: Computational validation.

    Science.gov (United States)

    Zahariev, Tsvetan K; Slavchov, Radomir I; Tadjer, Alia V; Ivanova, Anela N

    2014-04-15

    Fully atomistic molecular dynamics simulations were performed on liquid n-pentane, n-hexane, and n-heptane to derive an atomistic model for middle-chain-length alkanes. All simulations were based on existing molecular-mechanical parameters for alkanes. The computational protocol was optimized, for example, in terms of thermo- and barostat, to reproduce properly the properties of the liquids. The model was validated by comparison of thermal, structural, and dynamic properties of the normal alkane liquids to experimental data. Two different combinations of temperature and pressure coupling algorithms were tested. A simple differential approach was applied to evaluate fluctuation-related properties with sufficient accuracy. Analysis of the data reveals a satisfactory representation of the hydrophobic systems behavior. Thermodynamic parameters are close to the experimental values and exhibit correct temperature dependence. The observed intramolecular geometry corresponds to extended conformations domination, whereas the intermolecular structure demonstrates all characteristics of liquid systems. Cavity size distribution function was calculated from coordinates analysis and was applied to study the solubility of gases in hexane and heptane oils. This study provides a platform for further in-depth research on hydrophobic solutions and multicomponent systems.

  2. Fracture toughness from atomistic simulations: Brittleness induced by emission of sessile dislocations

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, D. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering

    1998-08-04

    Using atomistic simulations of crack response for intermetallic materials the author shows that when the emitted dislocations are sessile and stay in the immediate vicinity of the crack tip the emitted dislocations can actually lead to brittle failure. She present the results of an atomistic simulation study of the simultaneous dislocation emission and crack propagation process in this class of materials. She used a molecular statics technique with embedded atom (EAM) potentials developed for NiAl. The crystal structure of NiAl is the CsCl type (B2) with a lattice parameter of 0.287 nm, which is reproduced by the potential together with the cohesive energy and elastic constants. The compound stays ordered up to the melting point, indicating a strong tendency towards chemical ordering with a relatively high energy of the antiphase boundary (APB). As a result of this relatively large energy the dislocations of 1/2<111> type Burgers vectors imply a high energy and the deformation process occurs via the larger <100> type dislocations.

  3. Atomistic studies of dislocations in {alpha}-iron using bond-order potential

    Energy Technology Data Exchange (ETDEWEB)

    Mrovec, Matous; Elsaesser, Christian; Gumbsch, Peter [Fraunhofer-Institut fuer Werkstoffmechanik IWM, Freiburg (Germany); IZBS, Universitaet Karlsruhe, Karlsruhe (Germany)

    2010-07-01

    Macroscopic plastic behavior is closely linked to properties of dislocations at the nanometer scale. Direct experimental observations of the dislocation core region and of its changes during dislocation motion are unfortunately impossible and better understanding of these phenomena can be obtained only with the help of atomistic simulations. Recent atomistic studies of dislocations in iron have provided however very different outcomes, both in terms of atomic structures and energetics. The most likely reason of these large differences is a lack of reliable interatomic potentials, which would be able to describe adequately the atomic bonding and magnetic interactions in iron. In the present work we present studies of dislocations in {alpha}-iron using a bond-order potential, which is based on a tight-binding bond representation. The model is able to capture the directional character of bonds present in transition metals and includes a description of magnetic effects within the Stoner model of itinerant magnetism. We compare results of our simulations with available first-principles predictions as well as with predictions of other empirical interatomic potentials and discuss underlying causes of the differences.

  4. Comparison of atomistic and elasticity approaches for carbon diffusion near line defects in {alpha}-iron

    Energy Technology Data Exchange (ETDEWEB)

    Veiga, R.G.A., E-mail: rgaveiga@gmail.com [Universite de Lyon, INSA Lyon, Laboratoire MATEIS, UMR CNRS 5510, 25 Avenue Jean Capelle, F69621, Villeurbanne (France); Perez, M. [Universite de Lyon, INSA Lyon, Laboratoire MATEIS, UMR CNRS 5510, 25 Avenue Jean Capelle, F69621, Villeurbanne (France); Becquart, C.S. [Unite Materiaux et Transformations (UMET), Ecole Nationale Superieure de Chimie de Lille, UMR CNRS 8207, Bat. C6, F59655 Villeneuve d' Ascq Cedex (France); Laboratoire commun EDF-CNRS Etude et Modelisation des Microstructures pour le Vieillissement des Materiaux (EM2VM) (France); Clouet, E. [Service de Recherches de Metallurgie Physique, CEA/Saclay, 91191 Gif-sur-Yvette (France); Domain, C. [EDF, Recherche et Developpement, Materiaux et Mecanique des Composants, Les Renardieres, F77250 Moret sur Loing (France); Laboratoire commun EDF-CNRS Etude et Modelisation des Microstructures pour le Vieillissement des Materiaux (EM2VM) (France)

    2011-10-15

    Energy barriers for carbon migration in the neighborhood of line defects in body-centered cubic iron have been obtained by atomistic simulations. For this purpose, molecular statics with an Fe-C interatomic potential, based on the embedded atom method, has been employed. Results of these simulations have been compared to the predictions of anisotropic elasticity theory. The agreement is better for a carbon atom sitting on an octahedral site (energy minimum) than one on a tetrahedral site (saddle point). Absolute differences in the energy barriers obtained by the two methods are usually below 5 meV at distances larger than 1.5 nm from a screw dislocation and 2 nm (up to 4 nm in the glide plane) from the edge dislocation. Atomistic kinetic Monte Carlo simulations performed at T = 300 K and additional analysis based on the activation energies obtained by both methods show that they are in good qualitative agreement, despite some important quantitative discrepancies due to the large absolute errors found near the dislocation cores.

  5. HIV/AIDS and Alcohol

    Science.gov (United States)

    ... Psychiatric Disorders Other Substance Abuse HIV/AIDS HIV/AIDS Human immunodeficiency virus (HIV) targets the body’s immune ... and often leads to acquired immune deficiency syndrome (AIDS). Each year in the United States, between 55, ...

  6. HIV, AIDS, and the Future

    Science.gov (United States)

    Skip Navigation Bar Home Current Issue Past Issues HIV / AIDS HIV, AIDS, and the Future Past Issues / Summer 2009 ... turn Javascript on. Photo: The NAMES Project Foundation HIV and AIDS are a global catastrophe. While advances ...

  7. Political dimensions of AIDS.

    Science.gov (United States)

    Blewett, N

    1988-01-01

    World political aspects and the example of Australia as a national political response to AIDS are presented. Global policy on AIDS is influenced by the fact that the AIDS epidemic is the 1st to be largely predictable, that long lag times occur between intervention and measurable events, and by the prompt, professional leadership of WHO, lead by Dr. J. Mann. WHO began a Global Programme on AIDS in 1987, modelled on the responses of Canada and Australia. A world summit of Ministers of Health was convened in January 1988. These moves generated a response qualified by openness, cooperation, hope and common sense. The AIDS epidemic calls for unprecedented involvement of politicians: they must coordinate medical knowledge with community action, deal with public fear, exert strong, rational leadership and avoid quick, appealing counterproductive responses. 3 clear directions must be taken to deal with the epidemic: 1) strong research and education campaigns; 2) close contact with political colleagues, interest groups and the community; 3) a national strategy which enjoins diverse interest groups, with courage, rationality and compassion. In Australia, the AIDS response began with the unwitting infection of 3 infants by blood transfusion. A public information campaign emphasizing a penetrating TV ad campaign was instituted in 1987. Policy discussions were held in all parliamentary bodies. The AIDS epidemic demands rapid, creative responses, a break from traditions in health bureaucracy, continual scrutiny of funding procedures and administrative arrangements. In practical terms in Australia, this meant establishing a special AIDS branch within the Health Advancement Division of the Community Health Department. AIDS issues must remain depoliticized to defuse adversary politics and keep leaders in a united front.

  8. Aid and Growth

    DEFF Research Database (Denmark)

    Tarp, Finn; Mekasha, Tseday Jemaneh

    2013-01-01

    Recent litterature in the meta-analysis category where results from a range of studies are brought together throws doubt on the ability of foreign aid to foster economic growth and development. This article assesses what meta-analysis has to contribute to the litterature on the effectiveness...... of foreign aid in terms of growth impact. We re-examine key hypotheses, and find that the effect of aid on growth is positive and statistically significant. This significant effect is genuine, and not an artefact of publication selection. We also show why our results differ from those published elsewhere....

  9. Aid Supplies Over Time

    DEFF Research Database (Denmark)

    Jones, Edward Samuel

    2015-01-01

    What determines how much foreign aid donors provide? Existing answers to this question point to a complex range of influences. However, the tasks of distinguishing between long- and short-run factors, as well as differences between donors, have not been adequately addressed. Taking advantage...... of data spanning nearly 50 years, this paper uses panel cointegration techniques to consider these issues. The analysis provides clear evidence for heterogeneity both between donors and over time, bandwagon effects, and a growing influence of security considerations in aid provision. Domestic...... macroeconomic shocks have a moderate but delayed effect on aid disbursements....

  10. Aid and Growth

    DEFF Research Database (Denmark)

    Mekasha, Tseday Jemaneh; Tarp, Finn

    Some recent literature in the meta-analysis category where results from a range of studies are brought together throws doubt on the ability of foreign aid to foster economic growth and development. This paper assesses what meta-analysis has to say about the effectiveness of foreign aid in terms...... of the growth impact. We re-examine key hypotheses, and find that the effect of aid on growth is positive and statistically significant. This significant effect is genuine, and not an artefact of publication selection. We also show why our results differ from those published elsewhere....

  11. Tunable thermodynamic stability of Au-CuPt core-shell trimetallic nanoparticles by controlling the alloy composition: insights from atomistic simulations.

    Science.gov (United States)

    Huang, Rao; Shao, Gui-Fang; Wen, Yu-Hua; Sun, Shi-Gang

    2014-11-07

    A microscopic understanding of the thermal stability of metallic core-shell nanoparticles is of importance for their synthesis and ultimately application in catalysis. In this article, molecular dynamics simulations have been employed to investigate the thermodynamic evolution of Au-CuPt core-shell trimetallic nanoparticles with various Cu/Pt ratios during heating processes. Our results show that the thermodynamic stability of these nanoparticles is remarkably enhanced upon rising Pt compositions in the CuPt shell. The melting of all the nanoparticles initiates at surface and gradually spreads into the core. Due to the lattice mismatch among Au, Cu and Pt, stacking faults have been observed in the shell and their numbers are associated with the Cu/Pt ratios. With the increasing temperature, they have reduced continuously for the Cu-dominated shell while more stacking faults have been produced for the Pt-dominated shell because of the significantly different thermal expansion coefficients of the three metals. Beyond the overall melting, all nanoparticles transform into a trimetallic mixing alloy coated by an Au-dominated surface. This work provides a fundamental perspective on the thermodynamic behaviors of trimetallic, even multimetallic, nanoparticles at the atomistic level, indicating that controlling the alloy composition is an effective strategy to realize tunable thermal stability of metallic nanocatalysts.

  12. Lattice Thermal Conductivity of Ultra High Temperature Ceramics (UHTC) ZrB2 and HfB2 from Atomistic Simulations

    Science.gov (United States)

    Lawson, John W.; Daw, Murray S.; Bauschlicher, Charles W.

    2012-01-01

    Ultra high temperature ceramics (UHTC) including ZrB2 and HfB2 have a number of properties that make them attractive for applications in extreme environments. One such property is their high thermal conductivity. Computational modeling of these materials will facilitate understanding of fundamental mechanisms, elucidate structure-property relationships, and ultimately accelerate the materials design cycle. Progress in computational modeling of UHTCs however has been limited in part due to the absence of suitable interatomic potentials. Recently, we developed Tersoff style parameterizations of such potentials for both ZrB2 and HfB2 appropriate for atomistic simulations. As an application, Green-Kubo molecular dynamics simulations were performed to evaluate the lattice thermal conductivity for single crystals of ZrB2 and HfB2. The atomic mass difference in these binary compounds leads to oscillations in the time correlation function of the heat current, in contrast to the more typical monotonic decay seen in monoatomic materials such as Silicon, for example. Results at room temperature and at elevated temperatures will be reported.

  13. Pulmonary complications of AIDS: radiologic features. [AIDS

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, B.A.; Pomeranz, S.; Rabinowitz, J.G.; Rosen, M.J.; Train, J.S.; Norton, K.I.; Mendelson, D.S.

    1984-07-01

    Fifty-two patients with pulmonary complications of acquired immunodeficiency syndrome (AIDS) were studied over a 3-year period. The vast majority of the patients were homosexual; however, a significant number were intravenous drug abusers. Thirteen different organisms were noted, of which Pneumocystis carinii was by far the most common. Five patients had neoplasia. Most patients had initial abnormal chest films; however, eight patients subsequently shown to have Pneumocystis carinii pneumonia had normal chest films. A significant overlap in chest radiographic findings was noted among patients with different or multiple organisms. Lung biopsy should be an early consideration for all patients with a clinical history consistent with the pulmonary complications of AIDS. Of the 52 patients, 41 had died by the time this report was completed.

  14. Enhancement of Teaching and Learning of the Fundamentals of Nuclear Engineering Using Multimedia Courseware.

    Science.gov (United States)

    Keyvan, Shahla A.; Pickard, Rodney; Song, Xiaolong

    1997-01-01

    Computer-aided instruction incorporating interactive multimedia and network technologies can boost teaching effectiveness and student learning. This article describes the development and implementation of network server-based interactive multimedia courseware for a fundamental course in nuclear engineering. A student survey determined that 80% of…

  15. Materials Fundamentals of Gate Dielectrics

    CERN Document Server

    Demkov, Alexander A

    2006-01-01

    This book presents materials fundamentals of novel gate dielectrics that are being introduced into semiconductor manufacturing to ensure the continuous scalling of the CMOS devices. This is a very fast evolving field of research so we choose to focus on the basic understanding of the structure, thermodunamics, and electronic properties of these materials that determine their performance in device applications. Most of these materials are transition metal oxides. Ironically, the d-orbitals responsible for the high dielectric constant cause sever integration difficulties thus intrinsically limiting high-k dielectrics. Though new in the electronics industry many of these materials are wel known in the field of ceramics, and we describe this unique connection. The complexity of the structure-property relations in TM oxides makes the use of the state of the art first-principles calculations necessary. Several chapters give a detailed description of the modern theory of polarization, and heterojunction band discont...

  16. Polyhedral Scattering of Fundamental Monopoles

    CERN Document Server

    Battye, R; Rychenkova, P; Sutcliffe, P; Battye, Richard; Gibbons, Gary; Rychenkova, Paulina; Sutcliffe, Paul

    2003-01-01

    The dynamics of n slowly moving fundamental monopoles in the SU(n+1) BPS Yang-Mills-Higgs theory can be approximated by geodesic motion on the 4n-dimensional hyperkahler Lee-Weinberg-Yi manifold. In this paper we apply a variational method to construct some scaling geodesics on this manifold. These geodesics describe the scattering of n monopoles which lie on the vertices of a bouncing polyhedron; the polyhedron contracts from infinity to a point, representing the spherically symmetric n-monopole, and then expands back out to infinity. For different monopole masses the solutions generalize to form bouncing nested polyhedra. The relevance of these results to the dynamics of well separated SU(2) monopoles is also discussed.

  17. Silicon photonics fundamentals and devices

    CERN Document Server

    Deen, M Jamal

    2012-01-01

    The creation of affordable high speed optical communications using standard semiconductor manufacturing technology is a principal aim of silicon photonics research. This would involve replacing copper connections with optical fibres or waveguides, and electrons with photons. With applications such as telecommunications and information processing, light detection, spectroscopy, holography and robotics, silicon photonics has the potential to revolutionise electronic-only systems. Providing an overview of the physics, technology and device operation of photonic devices using exclusively silicon and related alloys, the book includes: * Basic Properties of Silicon * Quantum Wells, Wires, Dots and Superlattices * Absorption Processes in Semiconductors * Light Emitters in Silicon * Photodetectors , Photodiodes and Phototransistors * Raman Lasers including Raman Scattering * Guided Lightwaves * Planar Waveguide Devices * Fabrication Techniques and Material Systems Silicon Photonics: Fundamentals and Devices outlines ...

  18. Fundamentals of Condensed Matter Physics

    Science.gov (United States)

    Cohen, Marvin L.; Louie, Steven G.

    2016-05-01

    Part I. Basic Concepts: Electrons and Phonons: 1. Concept of a solid: qualitative introduction and overview; 2. Electrons in crystals; 3. Electronic energy bands; 4. Lattice vibrations and phonons; Part II. Electron Intercations, Dynamics and Responses: 5. Electron dynamics in crystals; 6. Many-electron interactions: the interacting electron gas and beyond; 7. Density functional theory; 8. The dielectric function for solids; Part III. Optical and Transport Phenomena: 9. Electronic transitions and optical properties of solids; 10. Electron-phonon interactions; 11. Dynamics of crystal electrons in a magnetic field; 12. Fundamentals of transport phenomena in solids; Part IV. Superconductivity, Magnetism, and Lower Dimensional Systems: 13. Using many-body techniques; 14. Superconductivity; 15. Magnetism; 16. Reduced-dimensional systems and nanostructures; Index.

  19. Queueing networks a fundamental approach

    CERN Document Server

    Dijk, Nico

    2011-01-01

    This handbook aims to highlight fundamental, methodological and computational aspects of networks of queues to provide insights and to unify results that can be applied in a more general manner.  The handbook is organized into five parts: Part 1 considers exact analytical results such as of product form type. Topics include characterization of product forms by physical balance concepts and simple traffic flow equations, classes of service and queue disciplines that allow a product form, a unified description of product forms for discrete time queueing networks, insights for insensitivity, and aggregation and decomposition results that allow subnetworks to be aggregated into single nodes to reduce computational burden. Part 2 looks at monotonicity and comparison results such as for computational simplification by either of two approaches: stochastic monotonicity and ordering results based on the ordering of the proces generators, and comparison results and explicit error bounds based on an underlying Markov r...

  20. Fundamental triangulation networks in Denmark

    Directory of Open Access Journals (Sweden)

    Borre Kai

    2014-04-01

    Full Text Available The first triangulation activity on Danish ground was carried out by the astronomer Tycho Brahe who resided on the island Hven. He wanted to determine the longitude difference of his observatory Uraniborg to Copenhagen. A by-product was a map of his island made in 1579. In 1761 the Royal Danish Academy of Sciences and Letters initiated a mapping project which should be based on the principle of triangulation. Eventually 24 maps were printed in varying scales, predominantly in 1:120 000. The last map was engraved in 1842. The Danish GradeMeasurement initiated remeasurements and redesign of the fundamental triangulation network. This network served scientific as well as cartographic purposes in more than a century. Only in the 1960s all triangulation sides were measured electronically. A combined least-squares adjustment followed in the 1970s

  1. Overview: Main Fundamentals for Steganography

    CERN Document Server

    AL-Ani, Zaidoon Kh; Zaidan, B B; Alanazi, Hamdan O

    2010-01-01

    The rapid development of multimedia and internet allows for wide distribution of digital media data. It becomes much easier to edit, modify and duplicate digital information .Besides that, digital documents are also easy to copy and distribute, therefore it will be faced by many threats. It is a big security and privacy issue, it become necessary to find appropriate protection because of the significance, accuracy and sensitivity of the information. Steganography considers one of the techniques which used to protect the important information. The main goals for this paper, to recognize the researchers for the main fundamentals of steganography. In this paper provides a general overview of the following subject areas: Steganography types, General Steganography system, Characterization of Steganography Systems and Classification of Steganography Techniques.

  2. Astronomical reach of fundamental physics.

    Science.gov (United States)

    Burrows, Adam S; Ostriker, Jeremiah P

    2014-02-18

    Using basic physical arguments, we derive by dimensional and physical analysis the characteristic masses and sizes of important objects in the universe in terms of just a few fundamental constants. This exercise illustrates the unifying power of physics and the profound connections between the small and the large in the cosmos we inhabit. We focus on the minimum and maximum masses of normal stars, the corresponding quantities for neutron stars, the maximum mass of a rocky planet, the maximum mass of a white dwarf, and the mass of a typical galaxy. To zeroth order, we show that all these masses can be expressed in terms of either the Planck mass or the Chandrasekar mass, in combination with various dimensionless quantities. With these examples, we expose the deep interrelationships imposed by nature between disparate realms of the universe and the amazing consequences of the unifying character of physical law.

  3. Phononic crystals fundamentals and applications

    CERN Document Server

    Adibi, Ali

    2016-01-01

    This book provides an in-depth analysis as well as an overview of phononic crystals. This book discusses numerous techniques for the analysis of phononic crystals and covers, among other material, sonic and ultrasonic structures, hypersonic planar structures and their characterization, and novel applications of phononic crystals. This is an ideal book for those working with micro and nanotechnology, MEMS (microelectromechanical systems), and acoustic devices. This book also: Presents an introduction to the fundamentals and properties of phononic crystals Covers simulation techniques for the analysis of phononic crystals Discusses sonic and ultrasonic, hypersonic and planar, and three-dimensional phononic crystal structures Illustrates how phononic crystal structures are being deployed in communication systems and sensing systems.

  4. Fundamentals of Protein NMR Spectroscopy

    CERN Document Server

    Rule, Gordon S

    2006-01-01

    NMR spectroscopy has proven to be a powerful technique to study the structure and dynamics of biological macromolecules. Fundamentals of Protein NMR Spectroscopy is a comprehensive textbook that guides the reader from a basic understanding of the phenomenological properties of magnetic resonance to the application and interpretation of modern multi-dimensional NMR experiments on 15N/13C-labeled proteins. Beginning with elementary quantum mechanics, a set of practical rules is presented and used to describe many commonly employed multi-dimensional, multi-nuclear NMR pulse sequences. A modular analysis of NMR pulse sequence building blocks also provides a basis for understanding and developing novel pulse programs. This text not only covers topics from chemical shift assignment to protein structure refinement, as well as the analysis of protein dynamics and chemical kinetics, but also provides a practical guide to many aspects of modern spectrometer hardware, sample preparation, experimental set-up, and data pr...

  5. Optical Metamaterials Fundamentals and Applications

    CERN Document Server

    Cai, Wenshan

    2010-01-01

    Metamaterials—artificially structured materials with engineered electromagnetic properties—have enabled unprecedented flexibility in manipulating electromagnetic waves and producing new functionalities. In just a few years, the field of optical metamaterials has emerged as one of the most exciting topics in the science of light, with stunning and unexpected outcomes that have fascinated scientists and the general public alike. This volume details recent advances in the study of optical metamaterials, ranging from fundamental aspects to up-to-date implementations, in one unified treatment. Important recent developments and applications such as superlenses and cloaking devices are also treated in detail and made understandable. Optical Metamaterials will serve as a very timely book for both newcomers and advanced researchers in this rapidly evolving field. Early praise for Optical Metamaterials: "...this book is timely bringing to students and other new entrants to the field the most up to date concepts. Th...

  6. Fundamentals of reversible flowchart languages

    DEFF Research Database (Denmark)

    Yokoyama, Tetsuo; Axelsen, Holger Bock; Glück, Robert

    2016-01-01

    . Although reversible flowcharts are superficially similar to classical flowcharts, there are crucial differences: atomic steps are limited to locally invertible operations, and join points require an explicit orthogonalizing conditional expression. Despite these constraints, we show that reversible......Abstract This paper presents the fundamentals of reversible flowcharts. They are intended to naturally represent the structure and control flow of reversible (imperative) programming languages in a simple computation model, in the same way classical flowcharts do for conventional languages......, structured reversible flowcharts are as expressive as unstructured ones, as shown by a reversible version of the classic Structured Program Theorem. We illustrate how reversible flowcharts can be concretized with two example programming languages, complete with syntax and semantics: a low-level unstructured...

  7. Molecular imaging. Fundamentals and applications

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Jie (ed.) [Chinese Academy of Sciences, Beijing (China). Intelligent Medical Research Center

    2013-07-01

    Covers a wide range of new theory, new techniques and new applications. Contributed by many experts in China. The editor has obtained the National Science and Technology Progress Award twice. ''Molecular Imaging: Fundamentals and Applications'' is a comprehensive monograph which describes not only the theory of the underlying algorithms and key technologies but also introduces a prototype system and its applications, bringing together theory, technology and applications. By explaining the basic concepts and principles of molecular imaging, imaging techniques, as well as research and applications in detail, the book provides both detailed theoretical background information and technical methods for researchers working in medical imaging and the life sciences. Clinical doctors and graduate students will also benefit from this book.

  8. Astronomical reach of fundamental physics

    Science.gov (United States)

    Burrows, Adam S.; Ostriker, Jeremiah P.

    2014-02-01

    Using basic physical arguments, we derive by dimensional and physical analysis the characteristic masses and sizes of important objects in the universe in terms of just a few fundamental constants. This exercise illustrates the unifying power of physics and the profound connections between the small and the large in the cosmos we inhabit. We focus on the minimum and maximum masses of normal stars, the corresponding quantities for neutron stars, the maximum mass of a rocky planet, the maximum mass of a white dwarf, and the mass of a typical galaxy. To zeroth order, we show that all these masses can be expressed in terms of either the Planck mass or the Chandrasekar mass, in combination with various dimensionless quantities. With these examples, we expose the deep interrelationships imposed by nature between disparate realms of the universe and the amazing consequences of the unifying character of physical law.

  9. Fundamentals of modern unsteady aerodynamics

    CERN Document Server

    Gülçat, Ülgen

    2016-01-01

    In this book, the author introduces the concept of unsteady aerodynamics and its underlying principles. He provides the readers with a comprehensive review of the fundamental physics of free and forced unsteadiness, the terminology and basic equations of aerodynamics ranging from incompressible flow to hypersonics. The book also covers modern topics related to the developments made in recent years, especially in relation to wing flapping for propulsion. The book is written for graduate and senior year undergraduate students in aerodynamics and also serves as a reference for experienced researchers. Each chapter includes ample examples, questions, problems and relevant references.   The treatment of these modern topics has been completely revised end expanded for the new edition. It now includes new numerical examples, a section on the ground effect, and state-space representation.

  10. Green Manufacturing Fundamentals and Applications

    CERN Document Server

    2013-01-01

    Green Manufacturing: Fundamentals and Applications introduces the basic definitions and issues surrounding green manufacturing at the process, machine and system (including supply chain) levels. It also shows, by way of several examples from different industry sectors, the potential for substantial improvement and the paths to achieve the improvement. Additionally, this book discusses regulatory and government motivations for green manufacturing and outlines the path for making manufacturing more green as well as making production more sustainable. This book also: • Discusses new engineering approaches for manufacturing and provides a path from traditional manufacturing to green manufacturing • Addresses regulatory and economic issues surrounding green manufacturing • Details new supply chains that need to be in place before going green • Includes state-of-the-art case studies in the areas of automotive, semiconductor and medical areas as well as in the supply chain and packaging areas Green Manufactu...

  11. HIV/AIDS

    Science.gov (United States)

    ... equity (covering the populations in need of services). Financing for sustainability (covering the costs of services). Innovation for acceleration (looking towards the future). WHO is a cosponsor of the Joint United Nations Programme on AIDS (UNAIDS). Within UNAIDS, WHO leads ...

  12. First Aid: Croup

    Science.gov (United States)

    ... Development Infections Diseases & Conditions Pregnancy & Baby Nutrition & Fitness Emotions & Behavior School & Family Life First Aid & Safety Doctors & ... with each breath has a pale or bluish color around the mouth drools or has difficulty swallowing ...

  13. Buying a Hearing Aid

    Science.gov (United States)

    ... Contact Us Calendar ENTCareers Marketplace ENT Careers Marketplace Log in b Log in Toggle navigation b Join Now Donate Now ... using your hearing aids in quiet surroundings, gradually building up to noisier environments. Then eventually work up ...

  14. HIV/AIDS

    Science.gov (United States)

    HIV stands for human immunodeficiency virus. It harms your immune system by destroying the white blood cells ... It is the final stage of infection with HIV. Not everyone with HIV develops AIDS. HIV most ...

  15. AidData

    Data.gov (United States)

    US Agency for International Development — AidData is a research and innovation lab making information on development finance more accessible and actionable. Tracking more than $6 trillion dollars from 90+...

  16. Convulsions - first aid - slideshow

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/presentations/100212.htm Convulsions - first aid - series—Procedure, part 1 To use ... slide 2 out of 2 Overview When a seizure occurs, the main goal is to protect the ...

  17. Hypophyseal pathology in AIDS

    OpenAIRE

    Mosca, L; Costanzi, G; Antonacci, C.; Boldorini, R; Carboni, N.; Cristina, S; Liberani, C.; Parravicini, C.; Pirolo, A.; Vago, L

    1992-01-01

    One hundred and eleven pituitary glands of patients (93 males, 18 females; mean age 32 years, 5 months) who died of fully developed AIDS or ARC were examined under light microscopy with the aid of immunohistochemistry. On post mortem (p.m.) examination a wide series of multiorgan alterations was noticed. Microscopically vanous lesions in both adeno- and neurohypophysis were seen. These ranged from vessel damage to secondaries to systemic infections, neoplas...

  18. Plasma-aided manufacturing

    Science.gov (United States)

    Shohet, J. L.

    1993-12-01

    Plasma-aided manufacturing is used for producing new materials with unusual and superior properties, for developing new chemical compounds and processes, for machining, and for altering and refining materials and surfaces. Plasma-aided manufacturing has direct applications to semiconductor fabrication, materials synthesis, welding, lighting, polymers, anti-corrosion coatings, machine tools, metallurgy, electrical and electronics devices, hazardous waste removal, high performance ceramics, and many other items in both the high-technology and the more traditional industries in the United States.

  19. THE AIDS HANDBOOK

    Directory of Open Access Journals (Sweden)

    Z Khan

    1997-12-01

    Full Text Available HIV infection and AIDS is increasingly becoming a major public health problem in our country. Currently, the reported cases represent only the 'tip of the iceberg' of the problem. In view of the fact that no cure or vaccine for the disease has yet been found, spreading knowledge and removing misconceptions is about the only way that AIDS can be effectively tackled.This handbook, developed by Prof. Shankar Chowdhury and associates, seeks to address all levels of medical and non-medical AIDS workers, as well as the layman. It deals with topics ranging from biology of the virus, symptoms and transmission of disease, to prevention, counselling for infected persons and action plan for AIDS education.The biology of the virus and the immune system is described in simple terms, as well as methods of testing for HIV, and what these test results mean. The progression of disease in adults and children, development of symptoms, diagnostic criteria for AIDS, treatment and outcome of disease is dealt with. How AIDS spreads between people, and the health risk for health workers and families is examined. The various ways in which transmission of HIV can be prevented is looked at in detail, including public health measures, national and internatonal action, and ethical and human rights issues involved.

  20. Atomistic simulation of the premelting of iron and aluminum : Implications for high-pressure melting-curve measurements

    NARCIS (Netherlands)

    Starikov, Sergey V.; Stegailov, Vladimir V.

    2009-01-01

    Using atomistic simulations we show the importance of the surface premelting phenomenon for the melting-curve measurements at high pressures. The model under consideration mimics the experimental conditions deployed for melting studies with diamond-anvil cells. The iron is considered in this work be

  1. Seminario latinoamericano de didactica de los medios audiovisuales (Latin American Seminar on Teaching with Audiovisual Aids).

    Science.gov (United States)

    Eduplan Informa, 1971

    1971-01-01

    This seminar on the use of audiovisual aids reached several conclusions on the need for and the use of such aids in Latin America. The need for educational innovation in the face of a new society, a new type of communication, and a new vision of man is stressed. A new definition of teaching and learning as a fundamental process of communication is…

  2. Multilateral Aid | L’aide multilatérale

    Directory of Open Access Journals (Sweden)

    2012-05-01

    Full Text Available Bilateral and Multilateral Aid, DAC Members, 1960–2010 (in million USD constant, 2009Aide bilatérale et multilatérale des pays membres du CAD, 1960-2010 (en millions USD constants de 2009­Bilateral and Multilateral Aid by Recipient Region, DAC Members, 2008 (in percentage of total aid by RegionAide bilatérale et multilatérale des pays membres du CAD par region de destination, 2008 (en pourcentage de l’aide totale par régionSources: OECD (2010 2010 DAC Report on Multilateral Aid (Paris: O...

  3. Fundamental degradation mechanisms of layered oxide Li-ion battery cathode materials: Methodology, insights and novel approaches

    Energy Technology Data Exchange (ETDEWEB)

    Hausbrand, R., E-mail: hausbrand@surface.tu-darmstadt.de; Cherkashinin, G.; Ehrenberg, H.; Gröting, M.; Albe, K.; Hess, C.; Jaegermann, W.

    2015-02-15

    Graphical abstract: - Highlights: • Description of recent in operando and in situ analysis methodology. • Surface science approach using photoemission for analysis of cathode surfaces and interfaces. • Ageing and fatigue of layered oxide Li-ion battery cathode materials from the atomistic point of view. • Defect formation and electronic structure evolution as causes for cathode degradation. • Significance of interfacial energy alignment and contact potential for side reactions. - Abstract: This overview addresses the atomistic aspects of degradation of layered LiMO{sub 2} (M = Ni, Co, Mn) oxide Li-ion battery cathode materials, aiming to shed light on the fundamental degradation mechanisms especially inside active cathode materials and at their interfaces. It includes recent results obtained by novel in situ/in operando diffraction methods, modelling, and quasi in situ surface science analysis. Degradation of the active cathode material occurs upon overcharge, resulting from a positive potential shift of the anode. Oxygen loss and eventual phase transformation resulting in dead regions are ascribed to changes in electronic structure and defect formation. The anode potential shift results from loss of free lithium due to side reactions occurring at electrode/electrolyte interfaces. Such side reactions are caused by electron transfer, and depend on the electron energy level alignment at the interface. Side reactions at electrode/electrolyte interfaces and capacity fade may be overcome by the use of suitable solid-state electrolytes and Li-containing anodes.

  4. A hybrid atomistic electrodynamics-quantum mechanical approach for simulating surface-enhanced Raman scattering.

    Science.gov (United States)

    Payton, John L; Morton, Seth M; Moore, Justin E; Jensen, Lasse

    2014-01-21

    Surface-enhanced Raman scattering (SERS) is a technique that has broad implications for biological and chemical sensing applications by providing the ability to simultaneously detect and identify a single molecule. The Raman scattering of molecules adsorbed on metal nanoparticles can be enhanced by many orders of magnitude. These enhancements stem from a twofold mechanism: an electromagnetic mechanism (EM), which is due to the enhanced local field near the metal surface, and a chemical mechanism (CM), which is due to the adsorbate specific interactions between the metal surface and the molecules. The local field near the metal surface can be significantly enhanced due to the plasmon excitation, and therefore chemists generally accept that the EM provides the majority of the enhancements. While classical electrodynamics simulations can accurately simulate the local electric field around metal nanoparticles, they offer few insights into the spectral changes that occur in SERS. First-principles simulations can directly predict the Raman spectrum but are limited to small metal clusters and therefore are often used for understanding the CM. Thus, there is a need for developing new methods that bridge the electrodynamics simulations of the metal nanoparticle and the first-principles simulations of the molecule to facilitate direct simulations of SERS spectra. In this Account, we discuss our recent work on developing a hybrid atomistic electrodynamics-quantum mechanical approach to simulate SERS. This hybrid method is called the discrete interaction model/quantum mechanics (DIM/QM) method and consists of an atomistic electrodynamics model of the metal nanoparticle and a time-dependent density functional theory (TDDFT) description of the molecule. In contrast to most previous work, the DIM/QM method enables us to retain a detailed atomistic structure of the nanoparticle and provides a natural bridge between the electronic structure methods and the macroscopic

  5. How Do Fundamental Christians Deal with Depression?

    Science.gov (United States)

    Spinney, Douglas Harvey

    1991-01-01

    Provides explanation of developmental dynamics in experience of fundamental Christians that provoke reactive depression. Describes depressant retardant defenses against depression that have been observed in Christian fundamental subculture. Suggests four counseling strategies for helping fundamentalists. (Author/ABL)

  6. Fundamentals and Techniques of Nonimaging

    Energy Technology Data Exchange (ETDEWEB)

    O' Gallagher, J. J.; Winston, R.

    2003-07-10

    This is the final report describing a long term basic research program in nonimaging optics that has led to major advances in important areas, including solar energy, fiber optics, illumination techniques, light detectors, and a great many other applications. The term ''nonimaging optics'' refers to the optics of extended sources in systems for which image forming is not important, but effective and efficient collection, concentration, transport, and distribution of light energy is. Although some of the most widely known developments of the early concepts have been in the field of solar energy, a broad variety of other uses have emerged. Most important, under the auspices of this program in fundamental research in nonimaging optics established at the University of Chicago with support from the Office of Basic Energy Sciences at the Department of Energy, the field has become very dynamic, with new ideas and concepts continuing to develop, while applications of the early concepts continue to be pursued. While the subject began as part of classical geometrical optics, it has been extended subsequently to the wave optics domain. Particularly relevant to potential new research directions are recent developments in the formalism of statistical and wave optics, which may be important in understanding energy transport on the nanoscale. Nonimaging optics permits the design of optical systems that achieve the maximum possible concentration allowed by physical conservation laws. The earliest designs were constructed by optimizing the collection of the extreme rays from a source to the desired target: the so-called ''edge-ray'' principle. Later, new concentrator types were generated by placing reflectors along the flow lines of the ''vector flux'' emanating from lambertian emitters in various geometries. A few years ago, a new development occurred with the discovery that making the design edge-ray a functional of some

  7. Virtual and composite fundamentals in the ERM

    NARCIS (Netherlands)

    Knot, KHW; Sturm, JE

    1999-01-01

    A latent-variable approach is applied to identify the appropriate driving process for fundamental exchange rates in the ERM. From the time-series characteristics of so-called "virtual fundamentals" and "composite fundamentals", a significant degree of mean reversion can be asserted. The relative deg

  8. Information physics fundamentals of nanophotonics.

    Science.gov (United States)

    Naruse, Makoto; Tate, Naoya; Aono, Masashi; Ohtsu, Motoichi

    2013-05-01

    Nanophotonics has been extensively studied with the aim of unveiling and exploiting light-matter interactions that occur at a scale below the diffraction limit of light, and recent progress made in experimental technologies--both in nanomaterial fabrication and characterization--is driving further advancements in the field. From the viewpoint of information, on the other hand, novel architectures, design and analysis principles, and even novel computing paradigms should be considered so that we can fully benefit from the potential of nanophotonics. This paper examines the information physics aspects of nanophotonics. More specifically, we present some fundamental and emergent information properties that stem from optical excitation transfer mediated by optical near-field interactions and the hierarchical properties inherent in optical near-fields. We theoretically and experimentally investigate aspects such as unidirectional signal transfer, energy efficiency and networking effects, among others, and we present their basic theoretical formalisms and describe demonstrations of practical applications. A stochastic analysis of light-assisted material formation is also presented, where an information-based approach provides a deeper understanding of the phenomena involved, such as self-organization. Furthermore, the spatio-temporal dynamics of optical excitation transfer and its inherent stochastic attributes are utilized for solution searching, paving the way to a novel computing paradigm that exploits coherent and dissipative processes in nanophotonics.

  9. Fundamental Scaling Laws in Nanophotonics.

    Science.gov (United States)

    Liu, Ke; Sun, Shuai; Majumdar, Arka; Sorger, Volker J

    2016-11-21

    The success of information technology has clearly demonstrated that miniaturization often leads to unprecedented performance, and unanticipated applications. This hypothesis of "smaller-is-better" has motivated optical engineers to build various nanophotonic devices, although an understanding leading to fundamental scaling behavior for this new class of devices is missing. Here we analyze scaling laws for optoelectronic devices operating at micro and nanometer length-scale. We show that optoelectronic device performance scales non-monotonically with device length due to the various device tradeoffs, and analyze how both optical and electrical constrains influence device power consumption and operating speed. Specifically, we investigate the direct influence of scaling on the performance of four classes of photonic devices, namely laser sources, electro-optic modulators, photodetectors, and all-optical switches based on three types of optical resonators; microring, Fabry-Perot cavity, and plasmonic metal nanoparticle. Results show that while microrings and Fabry-Perot cavities can outperform plasmonic cavities at larger length-scales, they stop working when the device length drops below 100 nanometers, due to insufficient functionality such as feedback (laser), index-modulation (modulator), absorption (detector) or field density (optical switch). Our results provide a detailed understanding of the limits of nanophotonics, towards establishing an opto-electronics roadmap, akin to the International Technology Roadmap for Semiconductors.

  10. Levitated Optomechanics for Fundamental Physics

    Science.gov (United States)

    Rashid, Muddassar; Bateman, James; Vovrosh, Jamie; Hempston, David; Ulbricht, Hendrik

    2015-05-01

    Optomechanics with levitated nano- and microparticles is believed to form a platform for testing fundamental principles of quantum physics, as well as find applications in sensing. We will report on a new scheme to trap nanoparticles, which is based on a parabolic mirror with a numerical aperture of 1. Combined with achromatic focussing, the setup is a cheap and readily straightforward solution to trapping nanoparticles for further study. Here, we report on the latest progress made in experimentation with levitated nanoparticles; these include the trapping of 100 nm nanodiamonds (with NV-centres) down to 1 mbar as well as the trapping of 50 nm Silica spheres down to 10?4 mbar without any form of feedback cooling. We will also report on the progress to implement feedback stabilisation of the centre of mass motion of the trapped particle using digital electronics. Finally, we argue that such a stabilised particle trap can be the particle source for a nanoparticle matterwave interferometer. We will present our Talbot interferometer scheme, which holds promise to test the quantum superposition principle in the new mass range of 106 amu. EPSRC, John Templeton Foundation.

  11. Fundamental Scaling Laws in Nanophotonics

    Science.gov (United States)

    Liu, Ke; Sun, Shuai; Majumdar, Arka; Sorger, Volker J.

    2016-11-01

    The success of information technology has clearly demonstrated that miniaturization often leads to unprecedented performance, and unanticipated applications. This hypothesis of “smaller-is-better” has motivated optical engineers to build various nanophotonic devices, although an understanding leading to fundamental scaling behavior for this new class of devices is missing. Here we analyze scaling laws for optoelectronic devices operating at micro and nanometer length-scale. We show that optoelectronic device performance scales non-monotonically with device length due to the various device tradeoffs, and analyze how both optical and electrical constrains influence device power consumption and operating speed. Specifically, we investigate the direct influence of scaling on the performance of four classes of photonic devices, namely laser sources, electro-optic modulators, photodetectors, and all-optical switches based on three types of optical resonators; microring, Fabry-Perot cavity, and plasmonic metal nanoparticle. Results show that while microrings and Fabry-Perot cavities can outperform plasmonic cavities at larger length-scales, they stop working when the device length drops below 100 nanometers, due to insufficient functionality such as feedback (laser), index-modulation (modulator), absorption (detector) or field density (optical switch). Our results provide a detailed understanding of the limits of nanophotonics, towards establishing an opto-electronics roadmap, akin to the International Technology Roadmap for Semiconductors.

  12. Fundamental studies of fusion plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Aamodt, R.E.; Catto, P.J.; D' Ippolito, D.A.; Myra, J.R.; Russell, D.A.

    1992-05-26

    The major portion of this program is devoted to critical ICH phenomena. The topics include edge physics, fast wave propagation, ICH induced high frequency instabilities, and a preliminary antenna design for Ignitor. This research was strongly coordinated with the world's experimental and design teams at JET, Culham, ORNL, and Ignitor. The results have been widely publicized at both general scientific meetings and topical workshops including the speciality workshop on ICRF design and physics sponsored by Lodestar in April 1992. The combination of theory, empirical modeling, and engineering design in this program makes this research particularly important for the design of future devices and for the understanding and performance projections of present tokamak devices. Additionally, the development of a diagnostic of runaway electrons on TEXT has proven particularly useful for the fundamental understanding of energetic electron confinement. This work has led to a better quantitative basis for quasilinear theory and the role of magnetic vs. electrostatic field fluctuations on electron transport. An APS invited talk was given on this subject and collaboration with PPPL personnel was also initiated. Ongoing research on these topics will continue for the remainder fo the contract period and the strong collaborations are expected to continue, enhancing both the relevance of the work and its immediate impact on areas needing critical understanding.

  13. IDDT: Fundamentals and Test Generation

    Institute of Scientific and Technical Information of China (English)

    KUANG JiShun(邝继顺); YOU ZhiQiang(尤志强); ZHU QiJian(朱启建); MIN YingHua(闵应骅)

    2003-01-01

    It is the time to explore the fundamentals of IDDT testing when extensive workhas been done for IDDT testing since it was proposed. This paper precisely defines the concept ofaverage transient current (IDDT) of CMOS digital ICs, and experimentally analyzes the feasibilityof IDDT test generation at gate level. Based on the SPICE simulation results, the paper suggests aformula to calculateIDDT by means of counting only logical up-transitions, which enablesIDDT testgeneration at logic level. The Bayesian optimization algorithm is utilized for IDDT test generation.Experimental results show that about 25% stuck-open faults are withIDDT testability larger than2.5, and likely to beIDDT testable. It is also found that most IDDT testable faults are located nearthe primary inputs of a circuit under test. IDDT test generation does not require fault sensitizationprocedure compared with stuck-at fault test generation. Furthermore, some redundant stuck-atfaults can be detected by using IDDT testing.

  14. Fluorescence lifetimes: fundamentals and interpretations.

    Science.gov (United States)

    Noomnarm, Ulai; Clegg, Robert M

    2009-01-01

    Fluorescence measurements have been an established mainstay of photosynthesis experiments for many decades. Because in the photosynthesis literature the basics of excited states and their fates are not usually described, we have presented here an easily understandable text for biology students in the style of a chapter in a text book. In this review we give an educational overview of fundamental physical principles of fluorescence, with emphasis on the temporal response of emission. Escape from the excited state of a molecule is a dynamic event, and the fluorescence emission is in direct kinetic competition with several other pathways of de-excitation. It is essentially through a kinetic competition between all the pathways of de-excitation that we gain information about the fluorescent sample on the molecular scale. A simple probability allegory is presented that illustrates the basic ideas that are important for understanding and interpreting most fluorescence experiments. We also briefly point out challenges that confront the experimenter when interpreting time-resolved fluorescence responses.

  15. A fundamental model of quasi-static wheelchair biomechanics.

    Science.gov (United States)

    Leary, M; Gruijters, J; Mazur, M; Subic, A; Burton, M; Fuss, F K

    2012-11-01

    The performance of a wheelchair system is a function of user anatomy, including arm segment lengths and muscle parameters, and wheelchair geometry, in particular, seat position relative to the wheel hub. To quantify performance, researchers have proposed a number of predictive models. In particular, the model proposed by Richter is extremely useful for providing initial analysis as it is simple to apply and provides insight into the peak and transient joint torques required to achieve a given angular velocity. The work presented in this paper identifies and corrects a critical error; specifically that the Richter model incorrectly predicts that shoulder torque is due to an anteflexing muscle moment. This identified error was confirmed analytically, graphically and numerically. The authors have developed a corrected, fundamental model which identifies that the shoulder anteflexes only in the first half of the push phase and retroflexes in the second half. The fundamental model has been extended by the authors to obtain novel data on joint and net power as a function of push progress. These outcomes indicate that shoulder power is positive in the first half of the push phase (concentrically contracting anteflexors) and negative in the second half (eccentrically contracting retroflexors). As the eccentric contraction introduces adverse negative power, these considerations are essential when optimising wheelchair design in terms of the user's musculoskeletal system. The proposed fundamental model was applied to assess the effect of vertical seat position on joint torques and power. Increasing the seat height increases the peak positive (concentric) shoulder and elbow torques while reducing the associated (eccentric) peak negative torque. Furthermore, the transition from positive to negative shoulder torque (as well as from positive to negative power) occurs later in the push phase with increasing seat height. These outcomes will aid in the optimisation of manual

  16. Mechanism of the Cassie-Wenzel transition via the atomistic and continuum string methods

    Energy Technology Data Exchange (ETDEWEB)

    Giacomello, Alberto, E-mail: alberto.giacomello@uniroma1.it; Casciola, Carlo Massimo [Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma “La Sapienza,” 00184 Rome (Italy); Meloni, Simone, E-mail: simone.meloni@epfl.ch [Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Müller, Marcus [Institut für Theoretische Physik, Georg-August-Universität Göttingen, 37077 Göttingen (Germany)

    2015-03-14

    The string method is a general and flexible strategy to compute the most probable transition path for an activated process (rare event). We apply here the atomistic string method in the density field to the Cassie-Wenzel transition, a central problem in the field of superhydrophobicity. We discuss in detail the mechanism of wetting of a submerged hydrophobic cavity of nanometer size and its dependence on the geometry of the cavity. Furthermore, we analyze the algorithmic analogies between the continuum “interface” string method and CREaM [Giacomello et al., Phys. Rev. Lett. 109, 226102 (2012)], a method inspired by the string that allows for a faster and simpler computation of the mechanism and of the free-energy profiles of the wetting process.

  17. Atomistic and continuums modeling of cluster migration and coagulation in precipitation reactions.

    Science.gov (United States)

    Warczok, Piotr; Ženíšek, Jaroslav; Kozeschnik, Ernst

    2012-07-01

    The influence of vacancy preference towards one of the constituents in a binary system on the formation of precipitates was investigated by atomistic and continuums modeling techniques. In case of vacancy preference towards the solute atoms, we find that the mobility of individual clusters as well as entire atom clusters is significantly altered compared to the case of vacancy preference towards the solvent atoms. The increased cluster mobility leads to pronounced cluster collisions, providing a precipitate growth and coarsening mechanism competitive to that of pure solute evaporation and adsorption considered in conventional diffusional growth and Ostwald ripening. A modification of a numerical Kampmann-Wagner type continuum model for precipitate growth is proposed, which incorporates the influence of both mechanisms. The prognoses of the modified model are validated against the growth laws obtained with lattice Monte Carlo simulations and a growth simulation considering solely the coalescence mechanism.

  18. Atomistic Investigation of Cu-Induced Misfolding in the Onset of Parkinson's Disease

    Science.gov (United States)

    Rose, Francis; Hodak, Miroslav; Bernholc, Jerry

    2009-03-01

    A nucleation mechanism for the misfolding of α-synuclein, the protein implicated in Parkinson's Disease (PD), is investigated using computer simulations. Through a combination of ab initio and classical simulation techniques, the conformational evolution of copper-ion-initiated misfolding of α-synuclein is determined. Based on these investigations and available experimental evidence, an atomistic model detailing the nucleation-initiated pathogenesis of PD is proposed. Once misfolded, the proteins can assemble into fibrils, the primary structural components of the deleterious PD plaques. Our model identifies a process of structural modifications to an initially unfolded α-synuclein that results in a partially folded intermediate with a well defined nucleation site as a precursor to the fully misfolded protein. The identified pathway can enable studies of reversal mechanisms and inhibitory agents, potentially leading to the development of effective therapies.

  19. An atomistic vision of the Mass Action Law: Prediction of carbon/oxygen defects in silicon

    Energy Technology Data Exchange (ETDEWEB)

    Brenet, G.; Timerkaeva, D.; Caliste, D.; Pochet, P. [CEA, INAC-SP2M, Atomistic Simulation Laboratory, F-38000 Grenoble (France); Univ. Grenoble Alpes, INAC-SP2M, L-Sim, F-38000 Grenoble (France); Sgourou, E. N.; Londos, C. A. [University of Athens, Solid State Physics Section, Panepistimiopolis Zografos, Athens 157 84 (Greece)

    2015-09-28

    We introduce an atomistic description of the kinetic Mass Action Law to predict concentrations of defects and complexes. We demonstrate in this paper that this approach accurately predicts carbon/oxygen related defect concentrations in silicon upon annealing. The model requires binding and migration energies of the impurities and complexes, here obtained from density functional theory (DFT) calculations. Vacancy-oxygen complex kinetics are studied as a model system during both isochronal and isothermal annealing. Results are in good agreement with experimental data, confirming the success of the methodology. More importantly, it gives access to the sequence of chain reactions by which oxygen and carbon related complexes are created in silicon. Beside the case of silicon, the understanding of such intricate reactions is a key to develop point defect engineering strategies to control defects and thus semiconductors properties.

  20. Atomistic study of energy funneling in the light-harvesting complex of green sulfur bacteria

    CERN Document Server

    Huh, Joonsuk; Brookes, Jennifer C; Valleau, Stéphanie; Fujita, Takatoshi; Aspuru-Guzik, Alán

    2013-01-01

    Phototrophic organisms such as plants, photosynthetic bacteria and algae use microscopic complexes of pigment molecules to absorb sunlight. Within the light-harvesting complexes, which frequently have multiple functional and structural subunits, the energy is transferred in the form of molecular excitations with very high efficiency. Green sulfur bacteria are considered to be amongst the most efficient light-harvesting organisms. Despite multiple experimental and theoretical studies of these bacteria the physical origin of the efficient and robust energy transfer in their light-harvesting complexes is not well understood. To study excitation dynamics at the systems level we introduce an atomistic model that mimic a complete light-harvesting apparatus of green sulfur bacteria. The model contains about 4000 pigment molecules and comprises a double wall roll for the chlorosome, a baseplate and six Fenna-Matthews-Olson trimer complexes. We show that the fast relaxation within functional subunits combined with the...

  1. Atomistic Simulations of Functional Au-144(SR)(60) Gold Nanoparticles in Aqueous Environment

    DEFF Research Database (Denmark)

    Heikkila, E.; Gurtovenko, A. A.; Martinez-Seara, H.

    2012-01-01

    Charged monolayer-protected gold nanoparticles (AuNPs) have been studied in aqueous solution by performing atomistic molecular dynamics simulations at physiological temperature (310 K). Particular attention has been paid to electrostatic properties that modulate the formation of a complex comprised...... of the nanoparticle together with surrounding ions and water. We focus on Au-144 nanoparticles that comprise a nearly spherical Au core (diameter similar to 2 nm), a passivating Au-S interface, and functionalized alkanethiol chains. Cationic and anionic AuNPs have been modeled with amine and carboxyl terminal groups...... potential displays a minimum for AuNP- at 1.9 nm from the center of the nanoparticle, marking a preferable location for Na+, while the AuNP+ potential (affecting the distribution of Cl-) rises almost monotonically with a local maximum. Comparison to Debye-Huckel theory shows very good agreement for radial...

  2. Structures, nanomechanics, and disintegration of single-walled GaN nanotubes: atomistic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Jeong Won; Hwang, Ho Jung; Song, Ki Oh; Choi, Won Young; Byun, Ki Ryang [Chung-Ang University, Seoul (Korea, Republic of); Kwon, Oh Keun [Semyung University, Jecheon (Korea, Republic of); Lee, Jun Ha [Sangmyung University, Chonan (Korea, Republic of); Kim, Won Woo [Juseong College, Cheongwon (Korea, Republic of)

    2003-09-15

    We have investigated the structural, mechanical, and thermal properties of single-walled GaN nanotubes by using atomistic simulations and a Tersoff-type potential. The Tersoff potential for GaN effectively describes the properties of GaN nanotubes. The nanomechanics of GaN nanotubes under tensile and compressive loadings have also been investigated, and Young's modulus has been calculated. The caloric curves of single-walled GaN nanotubes can be divided into three regions corresponding to nanotubes, the disintegrating range, and vapor. Since the stability or the stiffness of a tube decreases with increasing curving sheet-to-tube strain energy, the disintegration temperatures of GaN nanotubes are closely related to the curving sheet-to-tube strain energy.

  3. A Spectral Multiscale Method for Wave Propagation Analysis: Atomistic-Continuum Coupled Simulation

    CERN Document Server

    Patra, Amit K; Ganguli, Ranjan

    2014-01-01

    In this paper, we present a new multiscale method which is capable of coupling atomistic and continuum domains for high frequency wave propagation analysis. The problem of non-physical wave reflection, which occurs due to the change in system description across the interface between two scales, can be satisfactorily overcome by the proposed method. We propose an efficient spectral domain decomposition of the total fine scale displacement along with a potent macroscale equation in the Laplace domain to eliminate the spurious interfacial reflection. We use Laplace transform based spectral finite element method to model the macroscale, which provides the optimum approximations for required dynamic responses of the outer atoms of the simulated microscale region very accurately. This new method shows excellent agreement between the proposed multiscale model and the full molecular dynamics (MD) results. Numerical experiments of wave propagation in a 1D harmonic lattice, a 1D lattice with Lennard-Jones potential, a ...

  4. Computer code for the atomistic simulation of lattice defects and dynamics. [COMENT code

    Energy Technology Data Exchange (ETDEWEB)

    Schiffgens, J.O.; Graves, N.J.; Oster, C.A.

    1980-04-01

    This document has been prepared to satisfy the need for a detailed, up-to-date description of a computer code that can be used to simulate phenomena on an atomistic level. COMENT was written in FORTRAN IV and COMPASS (CDC assembly language) to solve the classical equations of motion for a large number of atoms interacting according to a given force law, and to perform the desired ancillary analysis of the resulting data. COMENT is a dual-purpose intended to describe static defect configurations as well as the detailed motion of atoms in a crystal lattice. It can be used to simulate the effect of temperature, impurities, and pre-existing defects on radiation-induced defect production mechanisms, defect migration, and defect stability.

  5. Mapping between atomistic simulations and Eshelby inclusions in the shear deformation of an amorphous silicon model

    Science.gov (United States)

    Albaret, T.; Tanguy, A.; Boioli, F.; Rodney, D.

    2016-05-01

    In this paper we perform quasistatic shear simulations of model amorphous silicon bulk samples with Stillinger-Weber-type potentials. Local plastic rearrangements identified based on local energy variations are fitted through their displacement fields on collections of Eshelby spherical inclusions, allowing determination of their transformation strain tensors. The latter are then used to quantitatively reproduce atomistic stress-strain curves, in terms of both shear and pressure components. We demonstrate that our methodology is able to capture the plastic behavior predicted by different Stillinger-Weber potentials, in particular, their different shear tension coupling. These calculations justify the decomposition of plasticity into shear transformations used so far in mesoscale models and provide atomic-scale parameters that can be used to limit the empiricism needed in such models up to now.

  6. Thermochemistry of organic reactions in microporous oxides by atomistic simulations: benchmarking against periodic B3LYP.

    Science.gov (United States)

    Bleken, Francesca; Svelle, Stian; Lillerud, Karl Petter; Olsbye, Unni; Arstad, Bjørnar; Swang, Ole

    2010-07-15

    The methylation of ethene by methyl chloride and methanol in the microporous materials SAPO-34 and SSZ-13 has been studied using different periodic atomistic modeling approaches based on density functional theory. The RPBE functional, which earlier has been used successfully in studies of surface reactions on metals, fails to yield a qualitatively correct description of the transition states under study. Employing B3LYP as functional gives results in line with experimental data: (1) Methanol is adsorbed more strongly than methyl chloride to the acid site. (2) The activation energies for the methylation of ethene are slightly lower for SSZ-13. Furthermore, the B3LYP activation energies are lower for methyl chloride than for methanol.

  7. Atomistic Study on Size Effects in Thermally Induced Martensitic Phase Transformation of NiTi

    Directory of Open Access Journals (Sweden)

    Sourav Gur

    2016-01-01

    Full Text Available The atomistic study shows strong size effects in thermally induced martensitic phase transformation evolution kinetics of equiatomic NiTi shape memory alloys (SMAs. It is shown that size effects are closely related to the presence of free surfaces; thus, NiTi thin films and nanopillars are studied. Quasi-static molecular dynamics simulations for several cell sizes at various (constant temperatures are performed by employing well-established interatomic potentials for NiTi. The study shows that size plays a crucial role in the evolution of martensite phase fraction and, importantly, can significantly change the phase transformation temperatures, which can be used for the design of NiTi based sensors, actuators, or devices at nano- to microscales. Interestingly, it is found that, at the nanometer scale, Richard’s equation describes very well the martensite phase fraction evolution in NiTi thin films and nanopillars as a function of temperature.

  8. Atomistic simulations of surface coverage effects in anisotropic wet chemical etching of crystalline silicon

    Energy Technology Data Exchange (ETDEWEB)

    Gosalvez, M.A.; Foster, A.S.; Nieminen, R.M

    2002-12-30

    Atomistic simulations of anisotropic wet chemical etching of crystalline silicon have been performed in order to determine the dependence of the etch rates of different crystallographic orientations on surface coverage and clustering of OH radicals. We show that the etch rate is a non-monotonic function of OH coverage and that there always exists a coverage value at which the etch rate reaches a maximum. The dependence of the anisotropy of the etching process on coverage, including the dependence of the fastest-etched plane orientation, is implicitly contained in the model and predictions of convex corner under-etching structures are made. We show that the whole etching process is controlled by only a few surface configurations involving a particular type of next-nearest neighbours. The relative value of the removal probabilities of these confitions determines the balance in the occurrence of step propagation and etch pitting for all surface orientations.

  9. Atomistic-Continuum Hybrid Simulation of Heat Transfer between Argon Flow and Copper Plates

    CERN Document Server

    Mao, Yijin; Chen, C L

    2016-01-01

    A simulation work aiming to study heat transfer coefficient between argon fluid flow and copper plate is carried out based on atomistic-continuum hybrid method. Navier-Stokes equations for continuum domain are solved through the Pressure Implicit with Splitting of Operators (PISO) algorithm, and the atom evolution in molecular domain is solved through the Verlet algorithm. The solver is validated by solving Couette flow and heat conduction problems. With both momentum and energy coupling method applied, simulations on convection of argon flows between two parallel plates are performed. The top plate is kept as a constant velocity and has higher temperature, while the lower one, which is modeled with FCC copper lattices, is also fixed but has lower temperature. It is found that, heat transfer between argon fluid flow and copper plate in this situation is much higher than that at macroscopic when the flow is fully developed.

  10. Collective dynamics in atomistic models with coupled translational and spin degrees of freedom

    Science.gov (United States)

    Perera, Dilina; Nicholson, Don M.; Eisenbach, Markus; Stocks, G. Malcolm; Landau, David P.

    2017-01-01

    Using an atomistic model that simultaneously treats the dynamics of translational and spin degrees of freedom, we perform combined molecular and spin dynamics simulations to investigate the mutual influence of the phonons and magnons on their respective frequency spectra and lifetimes in ferromagnetic bcc iron. By calculating the Fourier transforms of the space- and time-displaced correlation functions, the characteristic frequencies and the linewidths of the vibrational and magnetic excitation modes were determined. Comparison of the results with that of the stand-alone molecular dynamics and spin dynamics simulations reveals that the dynamic interplay between the phonons and magnons leads to a shift in the respective frequency spectra and a decrease in the lifetimes. Moreover, in the presence of lattice vibrations, additional longitudinal magnetic excitations were observed with the same frequencies as the longitudinal phonons.

  11. Coupling Lattice Boltzmann with Atomistic Dynamics for the multiscale simulation of nano-biological flows

    CERN Document Server

    Fyta, Maria; Kaxiras, Efthimios; Succi, Sauro

    2007-01-01

    We describe a recent multiscale approach based on the concurrent coupling of constrained molecular dynamics for long biomolecules with a mesoscopic lattice Boltzmann treatment of solvent hydrodynamics. The multiscale approach is based on a simple scheme of exchange of space-time information between the atomistic and mesoscopic scales and is capable of describing self-consistent hydrodynamic effects on molecular motion at a computational cost which scales linearly with both solute size and solvent volume. For an application of our multiscale method, we consider the much studied problem of biopolymer translocation through nanopores: we find that the method reproduces with remarkable accuracy the statistical scaling behavior of the translocation process and provides valuable insight into the cooperative aspects of biopolymer and hydrodynamic motion.

  12. Identifying early stage precipitation in large-scale atomistic simulations of superalloys

    Science.gov (United States)

    Schmidt, Eric; Bristowe, Paul D.

    2017-04-01

    A method for identifying and classifying ordered phases in large chemically and thermally disordered atomistic models is presented. The method uses Steinhardt parameters to represent local atomic configurations and develops probability density functions to classify individual atoms using naïve Bayes. The method is applied to large molecular dynamics simulations of supersaturated Ni-20 at% Al solid solutions in order to identify the formation of embryonic γ‧-Ni3Al. The composition and temperatures are chosen to promote precipitation, which is observed in the form of ordering and is found to occur more likely in regions with above average Al concentration producing ‘clusters’ of increasing size. The results are interpreted in terms of a precipitation mechanism in which the solid solution is unstable with respect to ordering and potentially followed by either spinodal decomposition or nucleation and growth.

  13. Atomistic study of deposition process of Al thin film on Cu substrate

    Energy Technology Data Exchange (ETDEWEB)

    Cao Yongzhi, E-mail: yzcaohit@gmail.com [Center for Precision Engineering, Harbin Institute of Technology, Harbin (China); Zhang Junjie; Sun Tao; Yan Yongda; Yu Fuli [Center for Precision Engineering, Harbin Institute of Technology, Harbin (China)

    2010-08-01

    In this paper we report molecular dynamics based atomistic simulations of deposition process of Al atoms onto Cu substrate and following nanoindentation process on that nanostructured material. Effects of incident energy on the morphology of deposited thin film and mechanical property of this nanostructured material are emphasized. The results reveal that the morphology of growing film is layer-by-layer-like at incident energy of 0.1-10 eV. The epitaxy mode of film growth is observed at incident energy below 1 eV, but film-mixing mode commences when incident energy increase to 10 eV accompanying with increased disorder of film structure, which improves quality of deposited thin film. Following indentation studies indicate deposited thin films pose lower stiffness than single crystal Al due to considerable amount of defects existed in them, but Cu substrate is strengthened by the interface generated from lattice mismatch between deposited Al thin film and Cu substrate.

  14. Atomistic study of lipid membranes containing chloroform: looking for a lipid-mediated mechanism of anesthesia.

    Directory of Open Access Journals (Sweden)

    Ramon Reigada

    Full Text Available The molecular mechanism of general anesthesia is still a controversial issue. Direct effect by linking of anesthetics to proteins and indirect action on the lipid membrane properties are the two hypotheses in conflict. Atomistic simulations of different lipid membranes subjected to the effect of small volatile organohalogen compounds are used to explore plausible lipid-mediated mechanisms. Simulations of homogeneous membranes reveal that electrostatic potential and lateral pressure transversal profiles are affected differently by chloroform (anesthetic and carbon tetrachloride (non-anesthetic. Simulations of structured membranes that combine ordered and disordered regions show that chloroform molecules accumulate preferentially in highly disordered lipid domains, suggesting that the combination of both lateral and transversal partitioning of chloroform in the cell membrane could be responsible of its anesthetic action.

  15. Aggregation behaviour of amphiphilic cyclodextrins: the nucleation stage by atomistic molecular dynamics simulations

    Science.gov (United States)

    Mazzaglia, Antonino; Ganazzoli, Fabio

    2015-01-01

    Summary Amphiphilically modified cyclodextrins may form various supramolecular aggregates. Here we report a theoretical study of the aggregation of a few amphiphilic cyclodextrins carrying hydrophobic thioalkyl groups and hydrophilic ethylene glycol moieties at opposite rims, focusing on the initial nucleation stage in an apolar solvent and in water. The study is based on atomistic molecular dynamics methods with a “bottom up” approach that can provide important information about the initial aggregates of few molecules. The focus is on the interaction pattern of amphiphilic cyclodextrin (aCD), which may interact by mutual inclusion of the substituent groups in the hydrophobic cavity of neighbouring molecules or by dispersion interactions at their lateral surface. We suggest that these aggregates can also form the nucleation stage of larger systems as well as the building blocks of micelles, vesicle, membranes, or generally nanoparticles thus opening new perspectives in the design of aggregates correlating their structures with the pharmaceutical properties. PMID:26734094

  16. NATO Advanced Study Institute on Surface Diffusion : Atomistic and Collective Processes

    CERN Document Server

    1997-01-01

    The interest in the problem of surface diffusion has been steadily growing over the last fifteen years. This is clearly evident from the increase in the number of papers dealing with the problem, the development of new experimental techniques, and the specialized sessions focusing on diffusion in national and international meetings. Part of the driving force behind this increasing activity is our recently acquired ability to observe and possibly control atomic scale phenomena. It is now possible to look selectively at individual atomistic processes and to determine their relative importance during growth and reactions at surfaces. The number of researchers interested in this problem also has been growing steadily which generates the need for a good reference source to farniliarize newcomers to the problem. While the recent emphasis is on the role of diffusion during growth, there is also continuing progress on the more traditional aspects of the problem describing mass transport in an ensemble of particles. S...

  17. Atomistic computer simulations of FePt nanoparticles. Thermodynamic and kinetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, M.

    2007-12-20

    In the present dissertation, a hierarchical multiscale approach for modeling FePt nanoparticles by atomistic computer simulations is developed. By describing the interatomic interactions on different levels of sophistication, various time and length scales can be accessed. Methods range from static quantum-mechanic total-energy calculations of small periodic systems to simulations of whole particles over an extended time by using simple lattice Hamiltonians. By employing these methods, the energetic and thermodynamic stability of non-crystalline multiply twinned FePt nanoparticles is investigated. Subsequently, the thermodynamics of the order-disorder transition in FePt nanoparticles is analyzed, including the influence of particle size, composition and modified surface energies by different chemical surroundings. In order to identify processes that reduce or enhance the rate of transformation from the disordered to the ordered state, the kinetics of the ordering transition in FePt nanoparticles is finally investigated by assessing the contributions of surface and volume diffusion. (orig.)

  18. Atomistic simulation study of linear alkylbenzene sulfonates at the water/air interface

    Science.gov (United States)

    He, Xibing; Guvench, Olgun; MacKerell, Alexander D.; Klein, Michael L.

    2010-01-01

    Molecular Dynamics simulations with the CHARMM atomistic force field have been used to study monolayers of a series of linear alkylbenzene sulfonates (LAS) at the water/air interface. Both the numbers of carbon atoms in the LAS alkyl tail (1 to 11), and the position of attachment of the benzene ring on the alkyl chain have been varied. Totally 36 LAS homologues and isomers have been investigated. The surface tensions of the systems and the average tilt angles of the LAS molecules are found to be related to both the length and the degree of branching of the alkyl tails, whereas the solubility and mobility are mostly determined by the tail length. PMID:20614916

  19. Long-time atomistic simulations with the Parallel Replica Dynamics method

    Science.gov (United States)

    Perez, Danny

    Molecular Dynamics (MD) -- the numerical integration of atomistic equations of motion -- is a workhorse of computational materials science. Indeed, MD can in principle be used to obtain any thermodynamic or kinetic quantity, without introducing any approximation or assumptions beyond the adequacy of the interaction potential. It is therefore an extremely powerful and flexible tool to study materials with atomistic spatio-temporal resolution. These enviable qualities however come at a steep computational price, hence limiting the system sizes and simulation times that can be achieved in practice. While the size limitation can be efficiently addressed with massively parallel implementations of MD based on spatial decomposition strategies, allowing for the simulation of trillions of atoms, the same approach usually cannot extend the timescales much beyond microseconds. In this article, we discuss an alternative parallel-in-time approach, the Parallel Replica Dynamics (ParRep) method, that aims at addressing the timescale limitation of MD for systems that evolve through rare state-to-state transitions. We review the formal underpinnings of the method and demonstrate that it can provide arbitrarily accurate results for any definition of the states. When an adequate definition of the states is available, ParRep can simulate trajectories with a parallel speedup approaching the number of replicas used. We demonstrate the usefulness of ParRep by presenting different examples of materials simulations where access to long timescales was essential to access the physical regime of interest and discuss practical considerations that must be addressed to carry out these simulations. Work supported by the United States Department of Energy (U.S. DOE), Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division.

  20. Atomic force microscope adhesion measurements and atomistic molecular dynamics simulations at different humidities

    Science.gov (United States)

    Seppä, Jeremias; Reischl, Bernhard; Sairanen, Hannu; Korpelainen, Virpi; Husu, Hannu; Heinonen, Martti; Raiteri, Paolo; Rohl, Andrew L.; Nordlund, Kai; Lassila, Antti

    2017-03-01

    Due to their operation principle atomic force microscopes (AFMs) are sensitive to all factors affecting the detected force between the probe and the sample. Relative humidity is an important and often neglected—both in experiments and simulations—factor in the interaction force between AFM probe and sample in air. This paper describes the humidity control system designed and built for the interferometrically traceable metrology AFM (IT-MAFM) at VTT MIKES. The humidity control is based on circulating the air of the AFM enclosure via dryer and humidifier paths with adjustable flow and mixing ratio of dry and humid air. The design humidity range of the system is 20–60 %rh. Force–distance adhesion studies at humidity levels between 25 %rh and 53 %rh are presented and compared to an atomistic molecular dynamics (MD) simulation. The uncertainty level of the thermal noise method implementation used for force constant calibration of the AFM cantilevers is 10 %, being the dominant component of the interaction force measurement uncertainty. Comparing the simulation and the experiment, the primary uncertainties are related to the nominally 7 nm radius and shape of measurement probe apex, possible wear and contamination, and the atomistic simulation technique details. The interaction forces are of the same order of magnitude in simulation and measurement (5 nN). An elongation of a few nanometres of the water meniscus between probe tip and sample, before its rupture, is seen in simulation upon retraction of the tip in higher humidity. This behaviour is also supported by the presented experimental measurement data but the data is insufficient to conclusively verify the quantitative meniscus elongation.

  1. Women and AIDS: introduction.

    Science.gov (United States)

    Krieger, N; Margo, G

    1991-01-01

    Around the world, more and more women--principally poor women of color--are being diagnosed with and are dying of AIDS, the acquired immune deficiency syndrome. Yet, effective and appropriate prevention programs for women are sorely missing from the global program to control AIDS. To help us understand why this gap exists, and what we must do to close it, the three articles in this issue focus on women and AIDS. Examining the situation in such countries as Zimbabwe and South Africa, as well as in other economically underdeveloped and developed regions, the authors argue that women with the least control over their bodies and their lives are at greatest risk of acquiring AIDS. For example, the high rate of infection among women in Africa cannot be understood apart from the legacy of colonialism (including land expropriation and the forced introduction of a migrant labor system) and the insidious combination of traditional and European patriarchal values. Only by recognizing the socioeconomic and cultural determinants of both disease and sexual behavior, and only by incorporating these insights into our AIDS prevention programs, will we be able to curb the spread of this lethal disease.

  2. AIDS in Africa.

    Science.gov (United States)

    Mokhobo, D

    1989-03-01

    Numerous cultural practices and attitudes in Africa represent formidable obstacles to the prevention of the further spread of acquired immunodeficiency syndrome (AIDS). Polygamy and concubinage are still widely practiced throughout Africa. In fact, sexual promiscuity on the part of males is traditionally viewed as positive--a reflection of male supremacy and male sexual prowess. The disintegration of the rural African family, brought about by urbanization, the migrant labor system, and poverty, has resulted in widespread premarital promiscuity. Contraceptive practices are perceived by many as a white conspiracy aimed at limiting the growth of the black population and thereby diminishing its political power. Condom use is particularly in disfavor. Thus, AIDS prevention campaigns urging Africans to restrict the number of sexual partners and to use condoms are unlikely to be successful. Another problem is that most Africans cannot believe that AIDS is sexually linked in that the disease does not affect the sex organs as is the case with other sexually transmitted diseases. The degree to which African governments are able to allocate resources to AIDS education will determine whether the epidemic can be controlled. Even with a massive outpouring of resources, it may be difficult to arouse public alarm about AIDS since Africans are so acclimated to living with calamities of every kind.

  3. AIDS ORPHANS GET SPECIAL VISITOR

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Chinese Premier Wen Jiabao visits AIDS orphans in Shangcai County,central China’s Henan Province,on November 30,a day before the 20th World AIDS Day. The region of Shangcai has the highest concentration of people living with HIV/AIDS in China. The Chinese Government has released a package of policies that offer people living with HIV/AIDS free medicine,health checks and consultations,as well as free schooling to AIDS orphans.

  4. Fundamental mechanisms of micromachine reliability

    Energy Technology Data Exchange (ETDEWEB)

    DE BOER,MAARTEN P.; SNIEGOWSKI,JEFFRY J.; KNAPP,JAMES A.; REDMOND,JAMES M.; MICHALSKE,TERRY A.; MAYER,THOMAS K.

    2000-01-01

    Due to extreme surface to volume ratios, adhesion and friction are critical properties for reliability of Microelectromechanical Systems (MEMS), but are not well understood. In this LDRD the authors established test structures, metrology and numerical modeling to conduct studies on adhesion and friction in MEMS. They then concentrated on measuring the effect of environment on MEMS adhesion. Polycrystalline silicon (polysilicon) is the primary material of interest in MEMS because of its integrated circuit process compatibility, low stress, high strength and conformal deposition nature. A plethora of useful micromachined device concepts have been demonstrated using Sandia National Laboratories' sophisticated in-house capabilities. One drawback to polysilicon is that in air the surface oxidizes, is high energy and is hydrophilic (i.e., it wets easily). This can lead to catastrophic failure because surface forces can cause MEMS parts that are brought into contact to adhere rather than perform their intended function. A fundamental concern is how environmental constituents such as water will affect adhesion energies in MEMS. The authors first demonstrated an accurate method to measure adhesion as reported in Chapter 1. In Chapter 2 through 5, they then studied the effect of water on adhesion depending on the surface condition (hydrophilic or hydrophobic). As described in Chapter 2, they find that adhesion energy of hydrophilic MEMS surfaces is high and increases exponentially with relative humidity (RH). Surface roughness is the controlling mechanism for this relationship. Adhesion can be reduced by several orders of magnitude by silane coupling agents applied via solution processing. They decrease the surface energy and render the surface hydrophobic (i.e. does not wet easily). However, only a molecular monolayer coats the surface. In Chapters 3-5 the authors map out the extent to which the monolayer reduces adhesion versus RH. They find that adhesion is

  5. Fundamentals of Physics, Student Study Guide, Extended 7th Edition

    Science.gov (United States)

    Halliday, David; Resnick, Robert; Walker, Jearl

    2004-06-01

    No other book on the market today can match the 30-year success of Halliday, Resnick and Walker's Fundamentals of Physics! Fundamentals of Physics, 7th Edition and the Extended Version, 7th Edition offer a solid understanding of fundamental physics concepts, helping readers apply this conceptual understanding to quantitative problem solving, in a breezy, easy-to-understand style. A unique combination of authoritative content and stimulating applications. * Numerous improvements in the text, based on feedback from the many users of the sixth edition (both instructors and students) * Several thousand end-of-chapter problems have been rewritten to streamline both the presentations and answers * 'Chapter Puzzlers' open each chapter with an intriguing application or question that is explained or answered in the chapter * Problem-solving tactics are provided to help beginning Physics students solve problems and avoid common error * The first section in every chapter introduces the subject of the chapter by asking and answering, "What is Physics?" as the question pertains to the chapter * Numerous supplements available to aid teachers and students The extended edition provides coverage of developments in Physics in the last 100 years, including: Einstein and Relativity, Bohr and others and Quantum Theory, and the more recent theoretical developments like String Theory.

  6. AIDS in Colombia.

    Science.gov (United States)

    Boshell, J; Gacharná, M G; García, M; Jaramillo, L S; Márquez, G; Fergusson, M M; González, S; Prada, E Y; de Rangel, R; de Cabas, R

    1989-01-01

    Between January 1984 and December 1987 a total of 178 AIDS cases were reported to the Colombian Ministry of Health. The location of these cases suggests that the human immunodeficiency virus (HIV) is widely distributed in Colombia. Most of those afflicted (97%) have been adult males. HIV seroprevalence studies of selected population groups revealed the highest antibody prevalence (5.65% in females, 22.5% in males) among individuals involved in high-risk behaviors who participated in a free AIDS testing program. High prevalences (from 0.6% to 3.9% in females, and 14.6% to 15.9% in males) were also found in patients (primarily female prostitutes and male homosexuals) attending clinics for sexually transmitted diseases in several urban areas. The number of AIDS cases in Colombia has doubled or tripled annually since reporting began in 1984, a pattern similar to that observed worldwide.

  7. [AIDS mortality in France].

    Science.gov (United States)

    Hatton, F; Maguin, P; Nicaud, V; Renaud, G

    1986-01-01

    A study about mortality by AIDS had been undertaken since July 1st 1983, in the Service of Information on Medical causes of Death (INSERM SC8), which is in charge of developing mortality statistics in France. From July 1st 1983 to September 30th 1985, 243 deaths due to AIDS were recorded. Only the cases where this diagnosis was clearly mentioned were selected; more than 90% were notified by hospitals and mainly by highly specialized services. The number of deaths, which was low and varied rather irregularly at the beginning, then increased by successive stages. The first year, during which a tenth of deaths was recorded every three months, was followed by a great increase, doubling, then tripling the initial numbers. Lastly, a second and sudden rise occurred during the third trimester of 1985, the trimestrial number of deaths due to AIDS reaching 80.

  8. Computer aided control engineering

    DEFF Research Database (Denmark)

    Szymkat, Maciej; Ravn, Ole

    1997-01-01

    Current developments in the field of Computer Aided Control Engineering (CACE) have a visible impact on the design methodologies and the structure of the software tools supporting them. Today control engineers has at their disposal libraries, packages or programming environments that may be speci......Current developments in the field of Computer Aided Control Engineering (CACE) have a visible impact on the design methodologies and the structure of the software tools supporting them. Today control engineers has at their disposal libraries, packages or programming environments that may...

  9. Astronomia Motivadora no Ensino Fundamental

    Science.gov (United States)

    Melo, J.; Voelzke, M. R.

    2008-09-01

    O objetivo principal deste trabalho é procurar desenvolver o interesse dos alunos pelas ciências através da Astronomia. Uma pesquisa com perguntas sobre Astronomia foi realizada junto a 161 alunos do Ensino Fundamental, com o intuito de descobrir conhecimentos prévios dos alunos sobre o assunto. Constatou-se, por exemplo, que 29,3% da 6ª série responderam corretamente o que é eclipse, 30,0% da 8ª série acertaram o que a Astronomia estuda, enquanto 42,3% dos alunos da 5ª série souberam definir o Sol. Pretende-se ampliar as turmas participantes e trabalhar, principalmente de forma prática com: dimensões e escalas no Sistema Solar, construção de luneta, questões como dia e noite, estações do ano e eclipses. Busca-se abordar, também, outros conteúdos de Física tais como a óptica na construção da luneta, e a mecânica no trabalho com escalas e medidas, e ao utilizar uma luminária para representar o Sol na questão do eclipse, e de outras disciplinas como a Matemática na transformação de unidades, regras de três; Artes na modelagem ou desenho dos planetas; a própria História com relação à busca pela origem do universo, e a Informática que possibilita a busca mais rápida por informações, além de permitir simulações e visualizações de imagens importantes. Acredita-se que a Astronomia é importante no processo ensino aprendizagem, pois permite a discussão de temas curiosos como, por exemplo, a origem do universo, viagens espaciais a existência ou não de vida em outros planetas, além de temas atuais como as novas tecnologias.

  10. Studying Aid: Some Methods

    NARCIS (Netherlands)

    D.R. Gasper (Des)

    2003-01-01

    textabstractINVESTIGATING IDEAS, IDEOLOGIES AND PRACTICES This paper presents some methods for trying to make sense of international aid and of its study.1 Some of the methods may be deemed ethnographic; the others are important partners to them, but rather different. In the course of discussing q

  11. Hearing Aids Communication

    DEFF Research Database (Denmark)

    Globally, hearing loss is the second most frequent disability. About 80% of the persons affected by hearing loss do not use hearing aids. The goal of this edited volume is to present a theoretically founded, interdisciplinary approach geared at understanding and improving social interaction impac...

  12. Parent Hearing Aid Experiences

    Science.gov (United States)

    Munoz, Karen; Roberts, Mallory; Mullings, Day; Harward, Richard

    2012-01-01

    This study addresses parent experiences in obtaining and managing hearing aids for their young child. The purpose was to identify challenges parents encounter to determine what state agencies can do to improve parent access to amplification. Data were collected July through September of 2010; 40 parents of children ages birth to 3 years old…

  13. Hearing Aid Personalization

    DEFF Research Database (Denmark)

    Nielsen, Jens Brehm; Nielsen, Jakob; Jensen, Bjørn Sand

    2013-01-01

    Modern digital hearing aids require and offer a great level of personalization. Today, this personalization is not performed based directly on what the user actually perceives, but on a hearing-care professional’s interpretation of what the user explains about what is perceived. In this paper, an...

  14. Computer Aided Lecturing.

    Science.gov (United States)

    Van Meter, Donald E.

    1994-01-01

    Surveyed students taking a natural resource conservation course to determine the effects of computer software that provides tools for creating and managing visual presentations to students. Results indicated that 94% of the respondents believed computer-aided lectures helped them and recommended their continued use; note taking was more effective,…

  15. AIDS and associated malignancies

    Institute of Scientific and Technical Information of China (English)

    Charles WOOD; William HARRINGTON Jr

    2005-01-01

    AIDS associated malignancies (ARL) is a major complication associated with AIDS patients upon immunosuppression.Chronically immunocompromised patients have a markedly increased risk of developing lymphoproliferative disease. In the era of potent antiretrovirals therapy (ARV), the malignant complications due to HIV- 1 infection have decreased in developed nations where ARV is administered, but still poses a major problem in developing countries where HIV- 1incidence is high and ARV is still not yet widely available. Even in ARV treated individuals there is a concern that the prolonged survival of many HIV- 1 carriers is likely to eventually result in an increased number of malignancies diagnosed.Malignancies that were found to have high incidence in HIV-infected individuals are Kaposi's sarcoma (KS), Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL). The incidence of NHL has increased nearly 200 fold in HIV-positive patients, and accounts for a greater percentage of AIDS defining illness in the US and Europe since the advent of HAART therapy. These AIDS related lymphomas are distinct from their counterparts seen in HIV- 1 seronegative patients.For example nearly half of all cases of ARL are associated with the presence of a gamma herpesvirus, Epstein Barr virus (EBV) or human herpesvirus-8 (HHV-8)/Kaposi's sarcoma associated herpesvirus (KSHV). The pathogenesis of ARLs is complex. B-cell proliferation driven by chronic antigenemia resulting in the induction of polyclonal and ultimately monoclonal lymphoproliferation may occur in the setting of severe immunosuppression.

  16. [Post-transfusional AIDS].

    Science.gov (United States)

    Azzini, M; Maccabruni, A; Marcellini, M; Michelone, G; Dei Cas, A

    1987-01-01

    Two cases of post-transfusional AIDS in two premature babies who received blood of the same seropositive donor, are reported. The risk of the susceptibility to HIV infection of these patients, in relation to the immaturity of immune system and to the transfusional treatment often necessary in premature newborns, is stressed.

  17. The CASPAR finding aids

    OpenAIRE

    Meghini, Carlo; Avancini, Henry; Versienti, Loredana

    2011-01-01

    One of the CASPAR key components is the FIND Components, which is implementing the Finding Aids of OAIS. According to OAIS, FIND manages Description Information that is associated to Information Packages in order to support the discovery of those Packages. FIND allows defining, creating, persisting, querying, browsing, and accessing both Description Information and the association between Information Packages and Description Information

  18. Coil Welding Aid

    Science.gov (United States)

    Wiesenbach, W. T.; Clark, M. C.

    1983-01-01

    Positioner holds coil inside cylinder during tack welding. Welding aid spaces turns of coil inside cylinder and applies contact pressure while coil is tack-welded to cylinder. Device facilitates fabrication of heat exchangers and other structures by eliminating hand-positioning and clamping of individual coil turns.

  19. Enteric parasites and AIDS

    Directory of Open Access Journals (Sweden)

    Sérgio Cimerman

    1999-11-01

    Full Text Available OBJECTIVE: To report on the importance of intestinal parasites in patients with AIDS, showing relevant data in the medical literature, with special emphasis on epidemiology, diagnosis and treatment of enteroparasitosis, especially cryptosporidiasis, isosporiasis, microsporidiasis and strongyloidiasis. DESIGN: Narrative review.

  20. STATE AID EVOLUTION OVERVIEW IN EUROPEAN UNION CONTEXT DURING THE PERIOD 2007-2012

    Directory of Open Access Journals (Sweden)

    Anca D.B., DODESCU

    2014-11-01

    Full Text Available According to the European Union point of view, the fundamental principle of state aid is to ensure that inside the single market, competition is not distorted. In this context, by exception state aid can be justified when they contribute to achieving EU's social and economic goals. This may take place when market forces obstruct the achieving of the proposed objectives or permit their achieving on unacceptable long terms and costs. This article is structured in four parts, focusing on European Union's vision regarding state aid measures. The first part of the article refers to the general context of state aid in EU. The second part of the article tries to define this concept according to European Commission point of view and also studies the state aid information provided by the EU, through its benchmarking instrument regarding state aid expenditure called State Aid Scoreboard. The third part of the article mainly presents the EU state aid evolution during the period 2007 - 2012 and establishes a methodological point of view in order to classify and divide state aid in two main categories: non-crisis state aid and crisis state aid, with the purpose of avoiding the distortion trends regarding state aid expenditure granted for the financial sector. This part of the article also presents different types of state aid at EU27 level and granted by the selected member states (Romania, Hungary, Bulgaria and Germany between 2007 and 2012 and also analysis horizontal aid, sectorial aid and state aid during the economic crisis 2008 - 2012, referring to recapitalization and asset relief measures and guarantees and liquidity measures. The last part of the article presents the conclusions and also states certain recommendations regarding EU state aid practices, based on the results obtained.

  1. Screening for AIDS.

    Science.gov (United States)

    1985-03-29

    Tests to detect serum antibody to human T-lymphotropic virus type III (HTLV-III), based on an enzyme-linked immunosorbent assay (ELISA) that uses whole disrupted HTLV-III virus antigens, are now commercially available in the US. Recent surveys of groups at high risk for acquired immunodeficiency syndrome (AIDS) have found that 22-65% of homosexual men, 87% of active intravenous drug users, 56-72% of hemophiliacs, and 35% of women who were sexual partners of men with AIDS have had postitive ELISA tests compared with fewer than 1% of those with no known risk factors. A positive ELISA test could be due to subclinical infection, immunity, or cross-reactivity with other viral antigens. Laboratory error can also produce false positive results. Thus, it is recommended that the ELISA test be repeated at least once on all seropositive specimens before the result is reported to the patient. The western blot test appears to be more specific and less sensitive than the ELISA. Studies of asymptomatic seropositive homosexual men followed for 2-5 years have found that over 50% remain asymptomatic, 5-19% develop full blown AIDS, and 25% develop signs suggestive of the AIDS-related complex. Asymptomatic patients with positive ELISA tests should be made aware of early signs and symptoms of AIDS. Other data suggest that seropositive patients have the HTLV-III virus in their blood, semen, and/or saliva and can transmit the infection. Precautions to prevent transmission, such as the use of condoms, should be taken by such patients. Physicians should be sensitive to the fear and anxiety that a positive ELISA test will create.

  2. Continuum Plate Theory and Atomistic Modeling to Find the Flexural Rigidity of a Graphene Sheet Interacting with a Substrate

    Directory of Open Access Journals (Sweden)

    M. W. Roberts

    2010-01-01

    Full Text Available Using a combination of continuum modeling, atomistic simulations, and numerical optimization, we estimate the flexural rigidity of a graphene sheet. We consider a rectangular sheet that is initially parallel to a rigid substrate. The sheet interacts with the substrate by van der Waals forces and deflects in response to loading on a pair of opposite edges. To estimate the flexural rigidity, we model the graphene sheet as a continuum and numerically solve an appropriate differential equation for the transverse deflection. This solution depends on the flexural rigidity. We then use an optimization procedure to find the value of the flexural rigidity that minimizes the difference between the numerical solutions and the deflections predicted by atomistic simulations. This procedure predicts a flexural rigidity of 0.26 nN nm=1.62 eV.

  3. Henan Surveys Blood Donors to Aid AIDS Prevention

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    Central China's Henan Province, one of the worst AIDS-hit provinces in the country, launched a sweeping survey in September of past blood donors to ascertain tile number of HIV-infected individuals to aid AIDS prevention and control work.

  4. Perceptions of Aid and Actual Aid in Intergenerational Caregiving.

    Science.gov (United States)

    Walker, Alexis J.; And Others

    1991-01-01

    Compared pairs (n=174) of elderly mothers' and their caregiving daughters' perceptions of aid given to the mothers with actual caregiving activities. Results indicated nearly half of the mothers and daughters were accurate in their perceptions of aid given to the mothers; when mothers' perception of aid was inaccurate, mothers overestimated rather…

  5. A Bayesian framework for adaptive selection, calibration, and validation of coarse-grained models of atomistic systems

    Energy Technology Data Exchange (ETDEWEB)

    Farrell, Kathryn, E-mail: kfarrell@ices.utexas.edu; Oden, J. Tinsley, E-mail: oden@ices.utexas.edu; Faghihi, Danial, E-mail: danial@ices.utexas.edu

    2015-08-15

    A general adaptive modeling algorithm for selection and validation of coarse-grained models of atomistic systems is presented. A Bayesian framework is developed to address uncertainties in parameters, data, and model selection. Algorithms for computing output sensitivities to parameter variances, model evidence and posterior model plausibilities for given data, and for computing what are referred to as Occam Categories in reference to a rough measure of model simplicity, make up components of the overall approach. Computational results are provided for representative applications.

  6. PF2fit: Polar Fast Fourier Matched Alignment of Atomistic Structures with 3D Electron Microscopy Maps.

    Directory of Open Access Journals (Sweden)

    Radhakrishna Bettadapura

    2015-10-01

    Full Text Available There continue to be increasing occurrences of both atomistic structure models in the PDB (possibly reconstructed from X-ray diffraction or NMR data, and 3D reconstructed cryo-electron microscopy (3D EM maps (albeit at coarser resolution of the same or homologous molecule or molecular assembly, deposited in the EMDB. To obtain the best possible structural model of the molecule at the best achievable resolution, and without any missing gaps, one typically aligns (match and fits the atomistic structure model with the 3D EM map. We discuss a new algorithm and generalized framework, named PF(2 fit (Polar Fast Fourier Fitting for the best possible structural alignment of atomistic structures with 3D EM. While PF(2 fit enables only a rigid, six dimensional (6D alignment method, it augments prior work on 6D X-ray structure and 3D EM alignment in multiple ways: Scoring. PF(2 fit includes a new scoring scheme that, in addition to rewarding overlaps between the volumes occupied by the atomistic structure and 3D EM map, rewards overlaps between the volumes complementary to them. We quantitatively demonstrate how this new complementary scoring scheme improves upon existing approaches. PF(2 fit also includes two scoring functions, the non-uniform exterior penalty and the skeleton-secondary structure score, and implements the scattering potential score as an alternative to traditional Gaussian blurring. Search. PF(2 fit utilizes a fast polar Fourier search scheme, whose main advantage is the ability to search over uniformly and adaptively sampled subsets of the space of rigid-body motions. PF(2 fit also implements a new reranking search and scoring methodology that considerably improves alignment metrics in results obtained from the initial search.

  7. Lattice Thermal Conductivity of Ultra High Temperature Ceramics ZrB2 and HfB2 from Atomistic Simulations

    Science.gov (United States)

    Lawson, John W.; Murray, Daw S.; Bauschlicher, Charles W., Jr.

    2011-01-01

    Atomistic Green-Kubo simulations are performed to evaluate the lattice thermal conductivity for single crystals of the ultra high temperature ceramics ZrB2 and HfB2 for a range of temperatures. Recently developed interatomic potentials are used for these simulations. Heat current correlation functions show rapid oscillations which can be identified with mixed metal-Boron optical phonon modes. Agreement with available experimental data is good.

  8. Fundamental challenges to methane recovery from gas hydrates

    Science.gov (United States)

    Servio, P.; Eaton, M.W.; Mahajan, D.; Winters, W.J.

    2005-01-01

    The fundamental challenges, the location, magnitude, and feasibility of recovery, which must be addressed to recover methane from dispersed hydrate sources, are presented. To induce dissociation of gas hydrate prior to methane recovery, two potential methods are typically considered. Because thermal stimulation requires a large energy input, it is less economically feasible than depressurization. The new data will allow the study of the effect of pressure, temperature, diffusion, porosity, tortuosity, composition of gas and water, and porous media on gas-hydrate production. These data also will allow one to improve existing models related to the stability and dissociation of sea floor hydrates. The reproducible kinetic data from the planned runs together with sediment properties will aid in developing a process to economically recover methane from a potential untapped hydrate source. The availability of plentiful methane will allow economical and large-scale production of methane-derived clean fuels to help avert future energy crises.

  9. What Is HIV/AIDS?

    Science.gov (United States)

    ... AIDS? Subscribe Translate Text Size Print What Is HIV/AIDS? Human Immunodeficiency Virus (HIV) HIV stands for human immunodeficiency virus. If left ... need medical treatment to prevent death. Where DId HIV Come From? Scientists identified a type of chimpanzee ...

  10. HIV / AIDS: An Unequal Burden

    Science.gov (United States)

    Skip Navigation Bar Home Current Issue Past Issues HIV / AIDS HIV / AIDS: An Unequal Burden Past Issues / Summer 2009 ... high-risk category, emphasizes Dr. Cargill. Photo: iStock HIV and Pregnancy Are there ways to help HIV- ...

  11. Does Corruption Cause Aid Fatigue?

    DEFF Research Database (Denmark)

    Bauhr, Monika; Charron, Nicholas; Nasiritousi, Naghmeh

    2013-01-01

    Does perceived corruption in recipient countries reduce support for foreign aid in donor countries? This under-explored yet salient question is examined using the 2009 Eurobarometer survey for the 27 EU countries. We suggest that perceived corruption can cause aid fatigue but that this relationship...... is highly contextualized. The results show that perceptions about corruption in developing countries reduce overall support for aid among respondents in donor countries. However, this effect is mitigated by country and contextual-level effects and different understandings of what we call the “aid-corruption...... paradox,” namely that the need for foreign aid is often the greatest in corrupt environments. Three different dynamics of the aid-corruption paradox influence support for aid: moral, pragmatic, and strategic understandings. In EU-15 countries, the effect of perceived corruption in recipient states on aid...

  12. Atomistic study of hydrogen embrittlement of grain boundaries in nickel: I. Fracture

    Science.gov (United States)

    Tehranchi, A.; Curtin, W. A.

    Hydrogen ingress into a metal is a persistent source of embrittlement. Fracture surfaces are often intergranular, suggesting favorable cleave crack growth along grain boundaries (GBs) as one driver for embrittlement. Here, atomistic simulations are used to investigate the effects of segregated hydrogen on the behavior of cracks along various symmetric tilt grain boundaries in fcc Nickel. An atomistic potential for Ni-H is first recalibrated against new quantum level computations of the energy of H in specific sites within the NiΣ5(120)⟨100⟩ GB. The binding energy of H atoms to various atomic sites in the NiΣ3(111) (twin), NiΣ5(120)⟨100⟩, NiΣ99(557)⟨110⟩, and NiΣ9(221)⟨110⟩ GBs, and to various surfaces created by separating these GBs into two possible fracture surfaces, are computed and used to determine equilibrium H concentrations at bulk H concentrations typical of embrittlement in Ni. Mode I fracture behavior is then studied, examining the influence of H in altering the competition between dislocation emission (crack blunting; "ductile" behavior) and cleavage fracture ("brittle" behavior) for intergranular cracks. Simulation results are compared with theoretical predictions (Griffith theory for cleavage; Rice theory for emission) using the computed surface energies. The deformation behavior at the GBs is, however, generally complex and not as simple as cleavage or emission at a sharp crack tip, which is not unexpected due to the complexity of the GB structures. In cases predicted to emit dislocations from the crack tip, the presence of H atoms reduces the critical load for emission of the dislocations and no cleavage is found. In the cases predicted to cleave, the presence of H atoms reduces the cleavage stress intensity and makes cleavage easier, including NiΣ9(221)⟨110⟩ which emits dislocations in the absence of H. Aside from the one unusual NiΣ9(221)⟨110⟩ case, no tendency is found for H to cause a ductile

  13. Atomistic modeling of nanowires, small-scale fatigue damage in cast magnesium, and materials for MEMS

    Energy Technology Data Exchange (ETDEWEB)

    Dunn, Martin L. [Univ. of Colorado, Boulder, CO (United States); Talmage, Mellisa J. [Univ. of Colorado, Boulder, CO (United States); McDowell, David L. [Georgia Inst. of Technology, Atlanta, GA (United States); West, Neil [Univ. of Colorado, Boulder, CO (United States); Gullett, Philip Michael [Mississippi State Univ., Mississippi State, MS (United States); Miller, David C. [Univ. of Colorado, Boulder, CO (United States); Spark, Kevin [Univ. of Colorado, Boulder, CO (United States); Diao, Jiankuai [Univ. of Colorado, Boulder, CO (United States); Horstemeyer, Mark F. [Mississippi State Univ., Mississippi State, MS (United States); Zimmerman, Jonathan A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Gall, K. [Georgia Inst. of Technology, Atlanta, GA (United States)

    2006-10-01

    Lightweight and miniaturized weapon systems are driving the use of new materials in design such as microscale materials and ultra low-density metallic materials. Reliable design of future weapon components and systems demands a thorough understanding of the deformation modes in these materials that comprise the components and a robust methodology to predict their performance during service or storage. Traditional continuum models of material deformation and failure are not easily extended to these new materials unless microstructural characteristics are included in the formulation. For example, in LIGA Ni and Al-Si thin films, the physical size is on the order of microns, a scale approaching key microstructural features. For a new potential structural material, cast Mg offers a high stiffness-to-weight ratio, but the microstructural heterogeneity at various scales requires a structure-property continuum model. Processes occurring at the nanoscale and microscale develop certain structures that drive material behavior. The objective of the work presented in this report was to understand material characteristics in relation to mechanical properties at the nanoscale and microscale in these promising new material systems. Research was conducted primarily at the University of Colorado at Boulder to employ tightly coupled experimentation and simulation to study damage at various material size scales under monotonic and cyclic loading conditions. Experimental characterization of nano/micro damage will be accomplished by novel techniques such as in-situ environmental scanning electron microscopy (ESEM), 1 MeV transmission electron microscopy (TEM), and atomic force microscopy (AFM). New simulations to support experimental efforts will include modified embedded atom method (MEAM) atomistic simulations at the nanoscale and single crystal micromechanical finite element simulations. This report summarizes the major research and development accomplishments for the LDRD project

  14. Atomistic simulation of the structure and elastic properties of gold nanowires

    Science.gov (United States)

    Diao, Jiankuai; Gall, Ken; Dunn, Martin L.

    2004-09-01

    We performed atomistic simulations to study the effect of free surfaces on the structure and elastic properties of gold nanowires aligned in the and crystallographic directions. Computationally, we formed a nanowire by assembling gold atoms into a long wire with free sides by putting them in their bulk fcc lattice positions. We then performed a static relaxation on the assemblage. The tensile surface stresses on the sides of the wire cause the wire to contract along the length with respect to the original fcc lattice, and we characterize this deformation in terms of an equilibrium strain versus the cross-sectional area. While the surface stress causes wires of both orientations and all sizes to increasingly contract with decreasing cross-sectional area, when the cross-sectional area of a nanowire is less than 1.83 nm×1.83 nm, the wire undergoes a phase transformation from fcc to bct, and the equilibrium strain increases by an order of magnitude. We then applied a uniform uniaxial strain incrementally to 1.2% to the relaxed nanowires in a molecular statics framework. From the simulation results we computed the effective axial Young's modulus and Poisson's ratios of the nanowire as a function of cross-sectional area. We used two approaches to compute the effective elastic moduli, one based on a definition in terms of the strain derivative of the total energy and another in terms of the virial stress often used in atomistic simulations. Both give quantitatively similar results, showing an increase in Young's modulus with a decrease of cross-sectional area in the nanowires that do not undergo a phase transformation. Those that undergo a phase transformation experience an increase of about a factor of three of Young's modulus. The Poisson's ratio of the wires that do not undergo a phase transformation show little change with the cross-sectional area. Those wires that undergo a phase transformation experience an increase of about 10% in Poisson's ratio. The wires show

  15. Protein Folding and Structure Prediction from the Ground Up: The Atomistic Associative Memory, Water Mediated, Structure and Energy Model.

    Science.gov (United States)

    Chen, Mingchen; Lin, Xingcheng; Zheng, Weihua; Onuchic, José N; Wolynes, Peter G

    2016-08-25

    The associative memory, water mediated, structure and energy model (AWSEM) is a coarse-grained force field with transferable tertiary interactions that incorporates local in sequence energetic biases using bioinformatically derived structural information about peptide fragments with locally similar sequences that we call memories. The memory information from the protein data bank (PDB) database guides proper protein folding. The structural information about available sequences in the database varies in quality and can sometimes lead to frustrated free energy landscapes locally. One way out of this difficulty is to construct the input fragment memory information from all-atom simulations of portions of the complete polypeptide chain. In this paper, we investigate this approach first put forward by Kwac and Wolynes in a more complete way by studying the structure prediction capabilities of this approach for six α-helical proteins. This scheme which we call the atomistic associative memory, water mediated, structure and energy model (AAWSEM) amounts to an ab initio protein structure prediction method that starts from the ground up without using bioinformatic input. The free energy profiles from AAWSEM show that atomistic fragment memories are sufficient to guide the correct folding when tertiary forces are included. AAWSEM combines the efficiency of coarse-grained simulations on the full protein level with the local structural accuracy achievable from all-atom simulations of only parts of a large protein. The results suggest that a hybrid use of atomistic fragment memory and database memory in structural predictions may well be optimal for many practical applications.

  16. How Do People Get AIDS?

    Science.gov (United States)

    ... of Healthy Breakfasts Shyness How Do People Get AIDS? KidsHealth > For Teens > How Do People Get AIDS? A A A en español ¿Cómo contrae alguien el SIDA? AIDS stands for acquired immunodeficiency syndrome , a disease that ...

  17. Fundamental Perspectives on Supply Chain Management

    NARCIS (Netherlands)

    Omta, S.W.F.; Hoenen, S.J.

    2012-01-01

    The aim of the present literature study is to find the fundamental perspectives/models in the realm of supply chain management and to investigate whether they can be extended based on recent literature findings. The fundamental perspectives were found using a two-tier snowball collection method, inc

  18. Fundamentals of Physics, Student's Solutions Manual

    Science.gov (United States)

    Halliday, David; Resnick, Robert; Walker, Jearl

    2000-07-01

    No other book on the market today can match the success of Halliday, Resnick and Walker's Fundamentals of Physics! In a breezy, easy-to-understand style the book offers a solid understanding of fundamental physics concepts, and helps readers apply this conceptual understanding to quantitative problem solving.

  19. Fundamentals of Physics, 7th Edition

    Science.gov (United States)

    Halliday, David; Resnick, Robert; Walker, Jearl

    2004-05-01

    No other book on the market today can match the 30-year success of Halliday, Resnick and Walker's Fundamentals of Physics! In a breezy, easy-to-understand style the book offers a solid understanding of fundamental physics concepts, and helps readers apply this conceptual understanding to quantitative problem solving. This book offers a unique combination of authoritative content and stimulating applications.

  20. Fundamentals of Physics, Problem Supplement No. 1

    Science.gov (United States)

    Halliday, David; Resnick, Robert; Walker, Jearl

    2000-05-01

    No other book on the market today can match the success of Halliday, Resnick and Walker's Fundamentals of Physics! In a breezy, easy-to-understand style the book offers a solid understanding of fundamental physics concepts, and helps readers apply this conceptual understanding to quantitative problem solving.